Can we shift this from being a "bah liberals!" thread to... anything else?
More like humans. Categorization of people and formation of groups is not an exclusively liberal disaease. Identity is part of the human condition. If you try to get rid of it, you are living a pipe dream.
In the end we are dealing with human nature itself, well known and proven to be rather nasty vs what it's not.
There are many old phrases used, some obviously frowned upon because some deem it as lumping folks into a group/pre-defining them such as "Birds of a feather flock together" yet at the same time it's true.
People are also subject to just going along with something because their friends/everyone is doing it. It's called peer pressue and we've all lived it at one time or another. Just think back about some of the things you've done yourselves.... And then see if you can recall "Why" and how far along you got swept up into it.
No one here was ever immune from that, myself included.
Speaking of those that act as modern social knights, I believe the current term is SJW. These are the literal footsoldiers of leftist movements that go out and do about anything they're told to. If not directly following instruction(s) they seek out opportunities to assault and batter "Because it's right" according to what they've been told - Can't say the right doesn't have it's share of these too because they do.
However these SJW's have been growing in numbers and aggressiveness as of late like the brownshirts did back in their day and I do hope we don't wind up with the same basic thing in the end they had when all was said and done.
Just good old human nature, that one thing you can rely one time and time again to be what it truly is.
We are our own worst enemy when it comes down to it.