I've run into this a few times and some "experts" make some of it up.
For example if I said something about lotr (which I often do) they would contradict me, thinking that I don't have a clue about lotr and when I ask them to prove it, they can't!
I think if you are an "expert" think about how you can prove it before you open your mouth! and I mean that in the happiest way possible