I've been on Facebook for three years now and have witnessed one brief fight on someone else's page but nothing on my own or in any conversations I've been part of - until the day before yesterday.
Person A was what I call a "courtesy friend": someone I know peripherally but don't hang out with at all. I actually intentionally limited my contact with her because whenever I talked to her she would tell me about some fight she'd gotten into with someone, which set off some alarm bells.
Anyway, the other day she posted about something she'd seen at Large Pet Products Store that made her mad. Everyone who responded, including me, replied that they thought it was uncool, also. Then one of Person A's friends, Person B, posted that NO ONE should EVER shop at ANY Large Pet Products Store because they are EVIL and SHE buys all her supplies at INDEPENDENT LOCAL places. She made frequent use of shrill, hysterical all caps.
I replied that I was stuck with Large Pet Products Store for reasons of volume and pricing. Person B proceeded to have an absolute name-calling, sanctimonious fit which included informing me that I'm living beyond my means, ruining the economy, setting a bad example, possibly poisoning my animals, and "bowing to my corporate overlords."
Person C then chimed in, calling me a *&@#*$ and a &*@#$@& and an ignorant %*^&@#.
Person A's silence and failure to address the nastiness spoke volumes even though she didn't post herself, and thus I unfriended her and no longer support the organization she runs, which I'd donated to previously.
All this over where I choose to buy cat food. I'm going to "bow to my corporate overlords" this Friday during my lunch hour and will be sure to buy something extra in honor of Person A, B, and C.