Paul Challenges All Who Judge Others To Consider What It Involves For Themselves (2:1-5).
‘For this reason you are without excuse, O man, whoever you are who judges, for in that in which you judge another, you condemn yourself, for you who are judging are practising the same things.'
‘For this reason' refers back to the previous argument about the many sins of mankind, and especially to the final verses of chapter 1. He wants his readers to recognise that what he has said there also applies to judges and philosophers, to Rabbis and to Jews, to people who felt themselves superior, or who might claim that they did retain God in their knowledge, and who were therefore prone to judge others. For the truth was that in spite of their superior attitudes they revealed themselves by their behaviour to be as guilty of the unrighteousnesses he has described as others. For they themselves did what they condemned in others.
Consequently being a judge or self-appointed adviser was a dangerous position to be in, because it meant that they were passing moral judgments on people, whilst overlooking or ignoring the fact that they themselves were guilty of the same things. By judging others, therefore, they condemned themselves, leaving themselves totally without any excuse. As James would have reminded them, ‘be not many teachers knowing that we will receive the greater condemnation, for in many things we all offend' (James 3:1-2).
Note that Paul's questions are addressed in the singular, as though speaking to one man. But the phrase ‘whoever you are who judges' brings out that it applies to the many. It has in mind all who pass judgment on others, each addressed personally.