Socrates and his relationship with the thirty

Socrates was good friends with many people in the thirty. The thirty was a group of wealthy elites who came to rule Athens. What does it say about Socrates that he was part of such an elite group? Plato was so determined to define “justice” in the Republic and he wrote about Socrates’ views of justice. However is Socrates really a reliable source to define justice when he associated with the thirty who were considered unjust by many people?