Once I realized how unreliable most people's beliefs are, the anxiety of accepting false information interferes too much with this "fun".

Are you sure that you're not being biased here? If people really are so unreliable, even when they are serious and upfront, how do they ever get anything done in practice?

Or could it be that you're failing to employ the standard heuristics for judging the reliability of people's claims? (Note that this also involves judging whether what's been said was even meant to be said authoritatively. People often say things without implying that they believe them firmly and on good evidence.)