I wholeheartedly feel that about the shame culture. That was everyone in my hometown. If you stood out, you were the asshole, you were the guy who thought he was better than everybody, you thought you were special, you were the snowflake and everybody would make actual effort to knock you down. I had never connected those dots but it kind of tracks that they aren't mutually exclusive. A sort of pessimism, both your own actions ("I can't dance") and toward others ("They're only doing that for attention. That prick thinks he's soo cool but nuh uh.") 
It follows too that negativity is easier than positivity. When I'm alone, I'm having imaginary arguments in my head, imagining telling someone what's what or making points about something that someone won't accept or something. Then I think "Why am I butthurt about literally nothing?" I think it's because bitterness comes from memory and positivity takes effort, making up the future is energy intensive, so we go to the easiest mindset to get the biggest rush. 
A joke gets less funny the more you hear it, we become immune to happiness in a sense. But anger is an endless flow of chemical stimulation of the brain. You can stay mad for a lifetime and I think all of these are part of why so many people do.