Interesting reflection. Learning empathy through experience in general can be very powerful - but the difference between becoming harmful in response or not, as a person, is still a bit of a mystery to me. I genuinely don’t know where good will comes from.

One rub - You mention the SEP - one thing that comes to mind: that involved group dynamics, and a situation where maintaining behavior neutrality (much less innate, naive “niceness”) is really impossible - the collective will of the group grew like an organism. But a lot of what you write about can also (even primarily) manifest in isolation, and even by design. (One of the first things that an abusive person will often do is start to dislocate the victim from a larger social group, isolate from friends/family, for example). This isn’t to disagree with anything above - only to suggest that a key context has to do with the nature of the interpersonal (eg intimate partner), and how that relates back to larger, more casual social interactions (eg work acquaintances).

Also, I think your point about the difference between nice and kind should be taught in every middle school curriculum - so important.