There's some NT hate in this thread..
In a way, I think it's deserved.
To explain the NT side of it,
The way I see it, as an NT, my brain is wired to do a lot of emotional 'checks'. There's a constant back and forth of "are you ok", "i'm ok", "are you ok", "i'm ok" - it's embedded in every line of conversation, every facial expression, every body gesture. I think of it like a flock of birds. As one bird moves, the whole flock moves with it. If one bird in that flock is independent and is able to act out, the whole flock loses its formation.
Maybe NT brains are wired this way because it's evolution's way of trying out a bird-like behaviour system on humans, wheras AS brains are wired more like that of cats and squirrels.
When I see someone with a facial expression that means 'I'm not ok' to me, my brain makes me NEED an explanation, especially if it's someone close to me. And if that expression turns out to be a false alarm, I feel that person is responsible for communicating the wrong emotion to me. At worst, it feels threatening to me because I am not able to have an emotional connection with that person. This makes me resentful of this person.
Now that I know that with AS people their facial expression isn't necessary reflective of their feelings or their intention, I'm able to control my gut reactions much better. But there is very little education on AS out there, and the learning takes a lot of work because it is not something that feels natural to NTs. The fundamental problem is that this society has stopped putting an emphasis on controlling feelings, and let us NTs run wild with it. It wasn't always like this. For example, Greek Stoics believed in having a tight control on emotions. I do think every NT should take a course on understanding the AS brain so we can learn to emphathize with AS people without relying on emotional communication.