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You really think this is just herd mentality with no help? It's possible, but I mean who the hell just wakes up and thinks, "We should start an irreverent agenda to promote segregation on Twitter today!"

Actually yes. There are studies showing that humans are extremely tribal and that emotion will almost always override rational thought in quite ridiculous ways. Search for "tribalism controls human behavior" or "emotion overriding rational thought" and you'll find some very interesting experiments.