Romans 2:1

It is important to point out that Paul is NOT defending the sinful actions. He just specified in the previous verse that they are rightfully punishable by death. What he is condemning here is the hypocrisy of simultaneously committing a sin and judging others for committing the same sin. Like Jesus said in Luke 6:42, we need to examine ourselves first and get rid of all our own sin before we will be in a position to criticize others. Honestly, how close are you to being free of all sin? Maybe that's too broad. Take instead just one of the Ten Commandments and consider how frequently or infrequently you disobey it, in any way whatsoever. (Remember Jesus' definition in Matthew 5:28 of breaking a Commandment by simply thinking about breaking it). Not sinless enough yet to judge another person?
I find it interesting that we are more likely to show mercy and compassion toward someone over their struggle with a sin if that sin is one we aren't struggling with ourselves. Often the more we struggle against a particular sin in our own lives, the more likely we are to condemn others for committing that same sin. Sin is sin, no matter who is involved in it. It is always wrong. We always need to fight against it. But we need to fight against it in our own lives so we can share our struggle with others, not look down on them while hiding our own failures.