Throughout Paul's talk about how everyone -- including people who judge others and even ourselves -- screwed up at least once, Paul brings up an important point regarding how God views our mistakes. The major point is that "there is no partiality with God." (2:11)
Partiality involves favoring one party over the other. While earthly judges may be prone to bias, God does not do that because partiality is unjust. As an example, Paul talked about how God evaluates both Jews and Gentiles (non-Jews) a few verses ago, and even though the Jews were supervised under God, they are still held to fair judgment as the Gentiles.