Summary: After listing all the bad sins of the world that deserve death in Romans 1, we must remember that we, in the church, are guilty of the same sins.
You can summarize the first two chapters of Romans this way: In the first chapter Paul says that people who do bad things are sinners. A lot of Christians can read the first chapter of Romans and feel pretty good about themselves. We'll say something like, "well, at least I'm not a murderer." Or, "I don't gossip...a lot..." There are something like 22 sins listed in this chapter.
Christian people tend to be loving, kind and generous people; they certainly are not God haters. So for us, Paul writes Romans chapter 2. In this chapter Paul teaches that good people are sinners, too.
Romans 2:1–11 (NKJV)
After looking at all the sins that we can get drawn into, we in the church must be very careful about getting on our high horse and condemning the world around us. The is one verse in the Bible we need to fully understand and know:
Romans 3:23 (NKJV) for all have sinned and fall short of the glory of God,
This verse applies equally to the most foul month murderer as well to the most saintly saint. We must realize that all have offended a most holy God. Paul is turning the tables around. In chapter one of Romans we can clearly see that it applies to oh so many in the world around us. Paul was writing to the Romans from the city of Corinth. Corinth was sin city. Corinth made Las Vegas look like a Sunday School Picnic. No doubt, Paul had seen it all. It is easy to point out the sins of the evil doers around us.
Paul uses a style of writing called the diatribe using question and answers to make a point. The unknown person Paul was referring to was probably representative of the Jews in Rome, and very possibly the pious and morally straight Gentile believer. I can hear the Jews and the morally straight and pious believers in Rome cheering Paul and saying "amen" to everything he said in chapter 1. But now Paul shift gears pick out a new target.
Romans 2:1 (NKJV) Therefore you are inexcusable, O man, whoever you are who judge, for in whatever you judge another you condemn yourself; for you who judge practice the same things.
In chapter 1 Paul was talking about those who had a natural revelation of God. That is the God we see in nature and the universe around us. It is even the God we see in moral conscience we display. This is something everyone in the world has experienced. However here in chapter 2, Paul is addressing those who not only have natural revelation, but special revelation has well. To the Jews, God chosen people, special revelation has been given. The believers in Rome had special revelation as well because they have heard the Gospel.
We also have God’s special revelation in that we have His word in our hand. Those that reject God, rejected His son Jesus, who is the subject of God’s special revelation, is at risk for the greater condemnation.
Now remember, Paul is talking to the believers in the church at Rome. Those who judge and condemn those in the world around us, will be judged by the same standards. But, wait a minute. I did not commit all the stuff listed in chapter 1.
According to the Believer’s Bible Commentary: The sins of cultured people are essentially the same as those of the heathen. Although a moralist may argue that he has not committed every sin in the book, he should remember the following facts:
1. He is capable of committing them all.
2. By breaking one commandment, he is guilty of all.
James 2:10 (NKJV) For whoever shall keep the whole law, and yet stumble in one point, he is guilty of all.
3. He has committed sins of thought which he may never have committed in actual deed, and these are forbidden by the word. Jesus taught that the lustful look, for instance, is tantamount to adultery 
Matthew 5:28 (NKJV) But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart.
Those in the church are guilty of sins of thought, word and deed. Are we any better, than those in chapter 1? This is what Paul is pointing out.
Romans 2:2–3 (NKJV) But we know that the judgment of God is according to truth against those who practice such things. 3 And do you think this, O man, you who judge those practicing such things, and doing the same, that you will escape the judgment of God?
God judges according to the truth. Many in the world claim to be moral, but who defines what is moral and what is not? God sets that standards. We were never asked to vote on what is moral. And herein lies the problem, the world’s definition of morality have crept into the church. Whether it is living together or having sex and babies outside the holy bonds of marriage, or watching senseless violence on the TV and having the world’s morality piped into our living rooms. We, who call ourselves Christians, are no better than the rest of world.