Again Paul answers the obvious question based on what he had just said. He said that God used the unrighteousness of man, specifically in the case of David, to show He is the one who changes the heart so that He is just when He declares a man innocent. The obvious question for those who love sin is why don't we just sin more, if God uses the sin of man to prove His faithfulness and righteousness? Should we not just pursue sin? The answer is obviously of course not. Increasing sin in the world is not a blessing, otherwise how could God judge the world. Just because our sin results in the glory of God doesn't mean that it is unjust for God to judge the sin. Because people don't understand (or don't want to understand) what Paul is saying, they pretend that he is pointing them to be greater sinners since God will use their great sin for His glory. Armenians continue to use this argument against Calvinists. If God is going to save who He is going to save, our sin doesn't matter. That is as much a lie now as it was at the time of David.