Protestants begin by (rightly) recognizing that it is an abomination to declare someone righteous who is in fact unrighteous. For a secular judge to do such a thing is a serious injustice, and there's no way God could do such an unjust thing, either. And yet, Romans 4:5 says God does the very thing He shouldn't be doing, God "justifies the ungodly". Looking at this conundrum, Protestants get to work trying to find an explanation for how God could do such a thing and not violate his Holiness. The "solution" they come up with (thinking this is in fact Paul's reasoning as well) is that God isn't declaring the unrighteous to be righteous out of thin air, but rather God is providing a basis to do so through the work of Jesus (citing Romans 3:21-26). They believe the sinners guilt gets imputed to Christ's account and Christ's perfect righteousness gets imputed to the sinner's account, so God can now look at the sinner's "criminal record" and see that not only has the punishment they deserve been satisfied, but the requirements of living a perfectly righteous life has been satisfied as well. Thus, God isn't violating His holiness at all when he declares the unrighteous to be righteous, in fact He's upholding His perfect standards. This is what Protestants think is "the Gospel".
This is where the faith versus works dichotomy then gets introduced: Protestants think (quite reasonably) that since we are unrighteous, all of our works are tainted by sin, and thus can have no place at all in justification. Instead, it can and must be all about Christ's work imputed to our account. This means that anyone at all attempting to introduce works into the salvation 'equation' is not only committing a serious abomination (by trying to get God to accept our imperfect works as righteousness), this person is also seriously deluded by not recognizing they are a miserable sinner with nothing but naked guilt standing before God's tribunal. This is why Protestants begin all their talks on the "Gospel" with an appeal to truly recognize you're a broken and miserable sinner who must look elsewhere, namely Christ alone, for your salvation.
While that version of the "Gospel" can sound plausible and appealing, it is in fact the furthest thing from historic and biblical Christianity. Nearly every aspect of the Protestant "Gospel" is tainted with serious error, both implicitly and explicitly. In his book A Biblical Defense of Catholicism, author and convert Dave Armstrong quotes a fellow convert, Al Kresta, who explains the heart of the problem quite masterfully:
Unlike the modern evangelical Protestant revivalistic preaching tradition, the Apostle Paul was not preoccupied with his acceptance as a sinner before a holy and righteous God. That was Luther's crisis. Protestants have tended to read Paul through the lens of Luther’s experience. ... Luther said he feared God but clung to the Apostle Paul. All the constitutive elements of the classic Luther-type experience, however, are missing in both the experience and the thought of the Apostle.
Unlike Luther, Paul was not preoccupied with his guilt, seeking reassurance of a gracious God. He was rather robust of conscience, even given to boasting, untroubled about whether God was gracious or not (Philippians 3:4 ff.; 2 Corinthians 10, 11). He knew God was gracious. He never pleads either with Jews or Gentiles to feel an anguished conscience and then receive release from that anguish in a message of forgiveness ... Paul’s burden is not to "bring people under conviction of sin" as in revival services. Forgiveness is simply a matter of fact.
When Paul speaks of himself as a serious sinner, it is ... very specifically because ... he had persecuted the church and missed God's new move - opening the covenant community to the Gentiles (1 Corinthians 15:9-10; Ephesians 3:8; Galatians 1:13-16; 1 Timothy 1:13-15). What is now set right in his life is not that he is no longer trying to work his way to heaven, abandons self-exertion and now trusts Christ; it is rather that he now sees that God has inexplicably chosen him to reveal this new and more inclusive covenant community made up of Jew and Gentile (Ephesians 2:11-3:6).What the Catholic apologist needs to realize is that Protestants are conflating Luther's experience with Paul's experience. Now, the main question to address at this point is what Paul meant when he says God "justifies the ungodly" in Romans 4:5. If this can be satisfactorily explained, then the force behind the Protestant "Gospel" is totally deflated. The answer to that question is surprisingly more simple and straightforward than most imagine.
Simply stated, for God to "justify the ungodly" means God reconciles the one who is alienated from Him. God does this by first forgiving their sins and by infusing His love and the Holy Spirit into their heart (Rom 5:5). God doesn't have to do any fancy legal maneuvers in order to justify us while maintaining His holiness, since that was never an issue. God is already merciful and ready to forgive, the Cross was the instrument by which God wanted this mercy to be manifested. The Cross was not about Christ taking our punishment, but it was about making Atonement (see This Article). Further, Christ didn't live a life of obedience in our place, but He did live a life of perfect obedience for us (see This Article). Of course it's an abomination for God to declare an unrighteous person to be righteous, which is why this never happens; that's a Protestant misinterpreting of the text.
The most astonishing thing about modern Protestant approaches to Romans 4:5 is that it goes against what the Pretend Reformers themselves had to say about it. They saw that Romans 4:5 clearly connects with 4:6-8 and is interpreted by it:
5 And to the one who does not work but believes in him who justifies the ungodly, his faith is counted as righteousness, 6 just as David also speaks of the blessing of the one to whom God counts righteousness apart from works: 7 “Blessed are those whose lawless deeds are forgiven, and whose sins are covered; 8 blessed is the man against whom the Lord will not count his sin.”I will let Luther and Calvin speak for themselves here. First from Calvin:
In the fourth chapter of the Epistle to the Romans, he [Paul] first terms it [justification] the imputation of righteousness, and hesitates not to place it in forgiveness of sins: “Even as David also describeth the blessedness of the man unto whom God imputeth righteousness without works, saying, Blessed are they whose iniquities are forgiven,” &c. (Rom. 4:6-8). There, indeed, he is not speaking of a part of justification, but of the whole. He declares, moreover, that a definition of it was given by David, when he pronounced him blessed who has obtained the free pardon of his sins. Whence it appears that this righteousness of which he speaks is simply opposed to judicial guilt. (Institutes, Book 3, Ch 11)And Luther says the same thing, in the following quotes given by a Reformed author named Brian Vickers:
At least in his interpretation of Romans 4:1-8, Luther does not view the imputation of righteousness and the non-imputation of sin as two distinct elements, but rather as synonymous concepts. Commenting on Psalm 32:1-2, Luther says: "Thus the man to whom these two evils (evil deeds and sins) are forgiven, behold, he is the man whom God regards as righteous. Hence it follows, 'Blessed is the man to whom the Lord imputes no iniquity.'" Luther adds: "It is the same thing, whether we say, "to whom God imputes righteousness' or, 'to whom the Lord does not impute sin,' that is, unrighteousness." Thus God imputing a person as righteous is, in this text, the same thing as God forgiving a person's sin. (Quoted in Jesus' Blood and Righteousness, pages 25-26)So there it is, straight from the mouth of the two most important Protestants in history. Thus, for God to "justify the ungodly" is principally about forgiving of sin, not about God declaring an unrighteous person to be righteous. Think of it as a stain being cleaned off a shirt, to count the shirt "clean" is equivalent to counting the shirt as having no stain (i.e. not imputing stain to the shirt). Thus as long as God is not legally imputing sin to the individual, this entails God is (also) legally reckoning them as righteous. The main problem with these quotes though is that they fail to realize there is a two-fold obliterating of sin: there is the clearing of a 'legal slate' along with an cleansing of the soul (e.g. see Psalm 32:2 b).
It is astonishing to see how often Protestants today disconnect their interpretation of Romans 4:5 with 4:6-8, as well as the rest of the chapter. They don't even realize that 'ungodly' here need not necessarily refer to 'unrighteousness', but rather being 'ungodly' with respect to the Mosaic Law. The word 'ungodly' in Greek means 'lawless', not following the law. This can refer to sinning in general, but it could also refer to someone lacking the Mosaic Law by being outside the covenant of Moses. This is precisely why Paul referred to the Gentiles as "sinners" as a category of persons outside the covenant (Gal 2:15). Thus, when Paul speaks of "justifying the ungodly," he very well could have been speaking of God "justifying the Gentile," which fits perfectly with the context and would come off very shocking to the audience at the time. Paul just got done making the jaw-dropping claim that God will justify the Gentiles along with the Jews in Romans 3, and in Romans 4 Paul appeals to two examples: Abraham being justified before circumcision (i.e. while Abraham was a gentile), and to David after he committed grave sins that excommunicated him from the covenant, making him effectively a gentile in God's sight (see especially Romans 2:25).
To conclude, when one stops and thinks about it, the Protestant reading of Romans 4:5 is a self contradiction: God is not declaring someone legally righteous who is in fact legally unrighteous in the Protestant scheme, for in the Protestant scheme God only declares righteous when there is a basis to do so, namely from Christ's righteousness imputed. Thus, even in the Protestant reading, what they are saying is "God declares righteous the one with righteousness in their account", so the whole 'shock factor' of God doing the unthinkable never actually takes place. The next time a Protestant tries to tell you what the Gospel is, mostly likely appealing to Romans 4:5, you can know how to respond in a way that will turn their whole world-view on its head.