When society describes something neutral or positive, it often uses the term as an identifier: I am a woman (neutral). I am an academic (positive). He is gifted (positive).
When something is perceived as negative, it should preferably not be used as an identifier. For a long time autism was described exclusively by professionals and non-autistic parents and therefore perceived as something negative. They did not want the identity of their children to be associated with a word they consider a disability. In autistic society, however, there seems to be a majority that identifies with their minds and accepts their autistic strengths.
If I can identify with my autism, it’s natural for me to say that I am autistic. I also identify myself as a woman.
People who do not see themselves as part of the binary gender system are unlikely to feel like a woman and do not want to be labeled as a woman. People who disagree with their autism diagnosis, or who can not see themselves described in it, or who perceive autism as something negative that hinders them, are better described as people with autism or something else.
Everyone should decide for themselves what they want to be called.
I only speak for myself. I am autistic. If you read this and have the same diagnosis, but not the same view, it is fine if you write for example “man with Autism” or anything else with which you can identify. I translate that in my head so that autistic people are meant.
When I write “autistic,” anyone in his or her mind can translate that I mean those who have an autistic brain. With all the advantages and disadvantages that may be involved.