What would change your belief?

The thing is that once we reach a conclusion we tend to stop thinking about it any more. Even if we do we tend to stick to our original conlusions as we ignore negative information and attend more to positive information.This coupled with our ability to hold two contradictory, even mutaully exclusive points in our head (ever loved and hated someone?) allows people to ignore that which does not fit in with our world view and attend to that which does all at once with limited cognitive dissonance.Google the confirmation bias.

That's exactly the cases. Funny things, people.