But in general, telling someone they've been a jerk all their life leads to certain existential crises that they will do just about anything to avoid.

People don't just get defensive, they get cruel. There's a whole group of tricks that are basically gaslighting the person. They take an aggressively "reasonable" stance and trying to convince the person they're crazy and it's all them.

Because this happens often enough that many of these 'overtures' are obvious, it makes interacting with moderates a waste of time. I've seen person after person get DDOSed by a handful of people throwing walls of text at them but really just tangenting the conversation off into oblivion.

So when someone who is actually in your group takes a moderate position, unless you know them personally, you can't know if they're really a moderate or just a troll. That's not to say you spend effort on people at the extremes, it just means you are hesitant about overly-moderate people the way you are about people asking you for help on a street corner. You've tried it before and it's a scam so often you don't even want to make eye contact.