To the outside, the difference is hard to tell, isn't it? Between neuro-diversity and genuine unpleasantness -- isn't it mostly that one has a diagnosis (that you know of) and the other does not?
You might change your moral judgement of someone's behavior if you find out they have this or that condition (at least I do), but it doesn't change how their behavior impacts you, does it? If it did, I think the best you could do is to assume that everyone has some sort of condition that makes them act the way they do, and it'll be less of a problem.
As someone who's neurodiverse myself, I do want to agree with this. Having said that, I do think it's possible for someone to choose to be an asshole and be neurodiverse at the same time. I wouldn't ever want my neurodiversity to be a free pass for any type of behaviour myself.
I generally struggle with the idea of someone actually choosing to be an asshole, I assume there's usually an unseen cause.
E.g. I work with someone who seems very normal, is very professional, and I have no reason to believe that they area neurodiverse in any way. They once were very direct in a ticket towards a different team. Did they choose to be an asshole, or were they losing their last ounce of patience and politeness because they've been carrying a mountain of responsibility and stress? I think it's very difficult to tell that apart, or to judge based on "well, they could have not taken on that responsibility so they're liable for anything that is a consequence of it".
I don't consider it a free pass, but there's a lot more understanding for things that are outside your control. Where we see that line of control probably determines whether we judge someone harshly or not.
You might change your moral judgement of someone's behavior if you find out they have this or that condition (at least I do), but it doesn't change how their behavior impacts you, does it? If it did, I think the best you could do is to assume that everyone has some sort of condition that makes them act the way they do, and it'll be less of a problem.