This is a pet peeve of mine, some bitter parent coming around and saying, "I know you don't know any better, but "person with autism" is more correct."
It's actually a political debate, not a matter of proper speech. People who think "person with autism" is better, think that autism is an aberration. I understand Person First language, I just don't think it fits with autism. My son can't detach "his autism", it's not a lead zepellin that holds him back from being a whole child. He's autistic, he's an autistic boy.
Pinched-face lady asks, "What's wrong with that boy? Why is like that?"
I answer, "He's autistic, that's the way he is."
You can say, "person with blond hair" or "that blonde", "that blonde boy". Have you ever heard, "that boy with red hair and freckles"? No! It's, "that !@#! redhead!"