> educated people will take everything you say literally and turn into missionaries
On the other hand, "Autistic" can and is taken literally regularly. So it feels pretty disingenuous for you to expect "educated people" to determine and keep track of how YOU specifically use the phrase compared to all the other people in their lives.
And if one of the people reading/hearing what you say IS autistic, their experience of others using the phrase is probably not as light-hearted as yours. There are plenty of people out there who DO mean it literally. So it is entirely up to the person reading/hearing the comment to make that determination.
You want to blast people in a professional setting who can't string together sentences, go for it. But describing them in a way that CAN be taken literally will cause problems.
TL;DR: My suggestion is to stick to "bad words" that people can't be born with.
Just paraphrasing OP as you seemed to miss the points he raised.
Anyway, what I've found is that people who speak out against "bad words" are quite toxic. It's obvious that autistic in this sense isn't the clinically diagnosed condition but in that of slang. If I say that you're like a pig, it doesn't mean that you go oink oink. And yet, educated people will take everything you say literally and turn into missionaries.
Reminds me of the time when the church destroyed pretty much every text on Greek philosophy simply because they said that the soul doesn't exist.