I'd say it's a little more rational. People have different life experiences and have reached different conclusions. When they see other people making claims which they "know" from experience to be wrong, they point them out and explain why. As a metaphor, imagine someone who doesn't live in your country making insulting and incorrect statements about it based on a combination of ignorant stereotypes and misinterpreted facts, long-disproven rumors, etc. You go correct them from a position of knowing more. It's the "someone is wrong on the internet" effect, cycling forever.

Also, yes, mentally ill people. I'm sure of it...