I agree that religion is an easy target, and not much of a test for rationality.

However I would be wary about the choice of harder targets, because some of them (politics especially) are things that a lot of people feel strongly about, which could make things messy here.

I think politics is a subject where everybody should try to overcome his own biases, but I would also prefer if OvercomingBias and LessWrong stayed politically neutral.