I have a pretty simple outlook. If I believe thing A and for lack of any objective proof one way or the other, somebody else claims to believe Thing B, I just naturally assume the other person is wrong. I don't like arguing or even strong discussions, so I probably wouldn't TELL them they're wrong or that I believe other wise than the way they believe but that's what I think. When there's a question, always assume the OTHER person is wrong. Maybe it's badness on their part. Maybe it's just blameless ignorance. Whatever it is, never doubt yourself.
Likewise, If I believe Thing A and EVERYBODY else claims to believe Thing B, I still never doubt myself, I just assume that they're ALL wrong, although I must admit it's possible that some of them don't really believe what they claim to believe and for reasons of their own, are lying. But that's their problem, not mine. Either way, I'm still right.
This viewpoint has carried me safely and calmly through many turbulent times. More people should adopt it.