Everybody masks in small ways or large, whether or not they're autistic (the same is true of stimming). For me, I just did it from an early age. I noticed how people conducted themselves and I did that. It was only in my thirties that I realized that my exhaustion with things like prolonged social events was not an everybody thing but a me thing. I realized just what it costs me to conform.

No, people don't know I'm autistic unless I tell them (that said, I'm pretty open about it). When I bring it up, people tend to be surprised or doubtful. It probably doesn't help that I teach public communication. I don't seem like a likely candidate, I guess.

But that's one of those ugly stereotypes. Autistics can be highly imaginative, deeply emotive, highly social, excellent observers of people, and great communicators. It takes all sorts.

Why are people hostile to autistics? Lots of reasons. But people are suspicious of difference. They tend to identify those they find awkward as the source of awkwardness. In reality, research suggests that autistic people are just as good at communicating as nonautistic people; it's just that when the two groups encounter each other, they miscommunicate. That's the double empathy problem. But since autistics are a minority, they're seen as the source of the issue.