For if the truth of God has increased through my lie to His glory, why am I also still judged as a sinner? And why not say, "Let us do evil that good may come"?—as we are slanderously reported and as some affirm that we say. Their condemnation is just. (Romans 3:7-8)
Some of the Jews thought that the apostle Paul minimized sin. They were concerned that if the Law of Moses were set aside, it would lead to people living however they wanted.
Here again, the heart of their objection was Paul’s doctrine of grace in his Law-free gospel. They thought he taught that sin did not matter. They viewed his gospel as being incapable of dealing with sin and thus promoting libertinism [live however you like]. - Pollard, Truth for Today Commentary, 109
Paul is quick to deny that he minimizes sin, and he vehemently denies that the gospel of Christ minimizes sin in any way.
Paul explicitly denies (3:8) that he encourages sin that God may be glorified. He will show also (6:1-8:17) that this is not the logical end of his teaching. - McGuiggan, Romans 113-114
Paul shows the inconsistencies in the Jew’s arguments against the message he proclaimed.
IF his [the hypothetical Jew] argument is true, then Paul is not a sinner, and neither for that matter are the Gentiles who the Jew so quickly condemned. For IF God is glorified by sin, then why not do all the evil we can commit, as per the Gentiles, so as to promote the glory of God? On the other hand, IF the Gentile is lost due to his disobedience, then so is the Jew who was disobedient to the law given unto him. - Wacaster, Studies in Romans, 109
Paul has already discussed the judgment of God at great length (Romans 2). The issue is not that Paul is minimizing sin - the issue is that the Jews thought God would treat their sin differently than the Gentile’s sin. Paul shows that this is not the case.
The gospel of Christ does not provide the Christian with a license to sin. Some of Paul’s audience argued that the logical conclusion of his teaching regarding the grace of God was that it didn’t matter how anyone lived.
Paul makes it clear this is not the case. Yes, the grace of God has appeared to all people (Titus 2:11). But this is not an excuse to live however we please.
God’s grace “teaches us” to live our lives for Him (Titus 2:12-14).
Amen!