That we're all either extremely good with math, technology, etc. or are very artistically gifted.
Heck, that we all have some sort of useful talent, skill, or interest. That just makes me feel worse about myself - I have no talents or skills, and my interests in Tool, Pokemon, and Hellraiser aren't ever going to get me anywhere.
That because I'm diagnosed with Asperger's syndrome, I must be very high-functioning and perfectly capable of anything an NT can do - the only reason I don't succeed is because I'm not trying hard enough. And there's no way I can possibly have selective mutism - I clearly just don't want to speak.
People saying that just about anything and everything either causes or can cure autism.
That we have no empathy. I have far more empathy than the average NT can even imagine, and am also somewhat empathic - I just don't know how to show it or how to make people feel better.
How every time there's a school shooting, people say the shooter had Asperger's/autism.
That we don't feel emotions. We just don't always show them the way they expect, that doesn't mean we don't feel them.
That all females on the spectrum are excellent mimics, have more socially acceptable interests, and are much less obviously affected than males on the spectrum (none of those are true for me).
That Asperger's is just an excuse to be rude/a jerk (I actually wish people would tell me if something I say comes off that way, so I know not to make the same mistake again - I hate upsetting people in any way).
That there isn't a difference between a meltdown and a tantrum.
That after we're out of school, we no longer need any sort of support - either we're magically "cured" or we just vanish (or so they act, anyway).
That we all lack imagination and didn't enjoy imaginative play as children. I loved to play pretend, far past when most NTs "grow out of" it - heck, I'd still love to if anyone would play with me and I weren't so self-conscious about not acting a part perfectly or the other person/people thinking my ideas were stupid.
That we all lack "theory of mind" - in fact, it seems to me that NTs are more often the ones lacking in that area.
And probably a bunch more I'm not thinking of at the moment.
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Yet in my new wildness and freedom I almost welcome the bitterness of alienage. For although nepenthe has calmed me, I know always that I am an outsider; a stranger in this century and among those who are still men.
-H. P. Lovecraft, "The Outsider"