Yes, I believe that since they are humans, and not gods, the Chorus is therefore biased. (In fact, even the Greek gods were quite biased).
The role of the Chorus in the Oedipus trilogy changes from play to play, but--in general--the Chorus is to be:
- the model audience: they are meant to be purged of pity and fear
- an intermediary between the actors and the audience: the Chorus filters, comments, amends, and clarifies for the audience
- moderate: the Greeks champion the epos megan ("the golden mean"), moderation in all things. The Chorus therefore attempts not to take sides, but to be reflective and impartial.
Having said that, the Chorus in Antigone, I believe, is very fickle. They side with Creon too much out of fear. They are almost complicit in the tragedy of Antigone, as they represent the paralyzed citizens who look the other way when a tyrant comes to power. Like Ismene, the Chorus does nothing to stop Creon's bullying or Antigone's death wish. Then, they change their view and side with Teiriseas once they realize that Creon has violated the will of the gods. In the end, their exemplum (moral comments at the ver end) sounds hypocritical.