I'm sorry for your bad experience but the word is only offensive if you take it that way.
When you tell people you're autistic, do you mean it as a bad thing or as a matter of fact? I'm guessing the latter, so take it the same way in the game: "Dude,are you autistic?" - "Yes, I am,thank you for asking." -they won't expect it, and you end the conversation there.
I do know what you mean,most people use it a negative way, but the negative way is NOT like a racial slur as much as it is like "are you stupid", or "are you retarded" (and note that retardation is also a possible medical condition) and as far as I know, calling somebody stupid isn't bannable, so neither should it be to call somebody autistic.
You could put being gay in the same field, because that's also common, people call each other fegs and feggots every other game, but I don't think that's bannable either, unless it goes too far. Now imagine if I got insulted because I'm actually gay and I don't want people to call me that? Plus, personal offence is exactly the thing people SHOULD NOT be banned for, everybody takes personal offense at something. What if I got attacked by a wolf once and I hate wolves, would it be okay for me to report every warwick I see? It would be ridiculous,the same way nobody can know that you're autistic and shouldn't be banned just because it happens to mean a lot to YOU.
In other words, don't turn the meaning of the word into something it's not, it's an insult to your gameplay, not your actual condition.