I suppose, beyond making fun of which is unacceptable, that some behaviour is considered "bad behaviour" if it would come from a "non-particular" person. People are highly sensitive to eye contact, voice tone and other subtleties to gage how the other person is feeling and how much of a threat they are. Similarly, overtaking conversations or appearing disinterested are also faux-pas in normal conversation and may indicate bad will or even a personality disorder.

As somebody who occasionally struggles to fit in socially, I have come to understand that I might come across in ways that do not reflect my inner feelings and that I need to add a bit more context and explanation, and just be more careful in general. You sort of have to help people to see where you're coming from to help them tune their social barometer somewhat sort of speaking.

At the extreme, you'd just start any conversation with "hey, I'm autistic, so if I appear a bit weird..." to hard-reset people's expectations and sooth their inner alarms. That is assuming they're decent folks acting in good faith.