And many people are offended or simply perplexed by "people with autism", so a lot of us just use whatever version comes out when it comes out given that a lot of us have enough trouble with language already. Personally I don't believe in DSM-style "autistic disorder" "Asperger disorder" etc labels so I'd never write that except when quoting a diagnostic manual or something. If I have to name them separately, I'd say autism or Asperger's, rather than acting like the DSM dictates what to call us. And the idea of any of these being things a person can "have" doesn't even make sense, so a lot of people don't use that terminology either.
Calling someone "autistic" is only bad if autism is somehow worse than, say, being female, where we get to be called a "woman" without fear of someone saying we're being "labeled". I will become strictly a "person with autism" on the same day I become strictly a "person with womanhood", and I hope we never sink so low as to get that afraid of what we are.
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"In my world it's a place of patterns and feel. In my world it's a haven for what is real. It's my world, nobody can steal it, but people like me, we live in the shadows." -Donna Williams