I think you're mistaking the relevance of his intentions as an excuse for him to continue being toxic. That's not the case at all. I think its very relevant why a person does the things they do. He still has to change and become less toxic no matter what.
If a person bullies because they have some kind of social ineptitude that makes them not realize they were bullying. That person is still a bully. However, its important to recognize if this was the case because the alternative is that he knew better and did it anyways because he knew he could get away with it.
> I don’t mean to be crude but it’s kind of irrelevant what the specific definition of bullying is, and it’s definitely irrelevant what his intentions were.
Why are intentions irrelevant? If someone is hurting me (or others), I do consider the question of whether they are doing so intentionally or inadvertently to be highly relevant to my judgement of their behaviour and how I am going to respond to it.
Ultimately even if you actually could not act any differently because of a disorder, others would still not be required to tolerate you. This is a consequence of being social animals, we set expectations for behavior and we enforce them. If you can’t play the game, you can’t exactly expect people who can to stop playing for your sake.