I never questioned my sanity once. Playing poker for a living at all stakes, you run into so many different characters. If I let dumb opinions affect me, I'd go insane.
Some posters won't admit they are or were wrong. They will still spin it in a way to make you look like you were or are in the wrong. If you happen to notice, I don't even bother engaging with those types. I admit when I am wrong, and I clarify that something is my opinion when it's my opinion, not fact. I am ok with being wrong; it usually means I learned something in the process, and I don't feel stupid or embarrassed.