convince themselves they believe in something that they really don't believe in.
Believe in something you don't really believe in?
Huh?
As for the thread title, it takes a special sort of brain damage to think that other people MUST be incapable of what you are, even if they affirm otherwise. A couple of posters here apparently can't even conceive that others could possibly sincerely believe something they can't, and it really bakes their noodles, doesn't it?
BTS