There is an excellent paper by Tyler Cowen and Robin Hanson that discusses how to deal with self-deception. I have a longer blog post on it, but here is the most important bit:
For a truth-seeker, the key question must be how sure you can be that you, at the moment, are substantially more likely to have a truth-seeking, in-control, rational core than the people you now disagree with. This is because if either of you have some substantial degree of meta-rationality, then your relative intelligence and information are largely irrelevant except as they may indicate which of you is more likely to be self-deceived about being meta-rational.
Akshat Rathi 