I see where you're coming from. I feel that joke comments that detail a whole thread I'd like to have discussion in is extremely frustrating. I sometimes wish they'd be banned, they're not adding anything to the post, except... Maybe it's helpful to people from becoming utterly hopeless and cynical.
I've thought about your point a decent amount of time for a few years and my thoughts are: people will people. It's for moderation teams to set rules and lead by example and clean up messes, if users refuse to self mod. Sometimes dogpiling is that, other times just disagreement that agrees with someone else's reasoning. Other times, it's just validation seeking because people have no firm seld-identity and/or core beliefs. Maybe they'll develop them if something really resonates, all exceptions acknowledged and considered. We don't learn from being correct very often. We do by being incorrect, or finding exceptions that ~~flour~~ flout our ideals.