I would have to agree. I'm not really well-versed in the autism subject but I assume it's like ADD or ADHD where doctors diagnose kids with it because it is easier than telling their crazy parents they failed at raising a child. I know a few people with autism and they wouldn't even be able to use a computer. If you seem like a normal person with just a bit of social awkwardness or stupidity you probably are just a stupid socially awkward normal person.
To my knowledge, the difference lies in that autism is the most severe form of ASD (autism spectrum disorder). ASD is a range of neurodevelopment disorders, with PDD-NOS (I think) being the less severe and Autistic Disorder being the most, but with each level on the spectrum varying from individual to individual. It is neurological.
ADD and ADHD are developmental disorders as well, but there is little neurological backing to the illness. There are common trends, but nothing had really been solidified. And because testing is done in an office, and the "signs" lie parallel to usually common behavior, someone exhibiting typical traits (Coupled with a doctor who doesn't care, or a parent who is convinced there is something wrong with their child, etc.) could easily be diagnosed with it (And more often than not are).
The above is to the best of my understanding. Personally, I don't think one should be trying to insult people in the first place, but if they should, using "autistic" as an insult only discredits their knowledge on the subject. Just like any other derogatory term one could use that doubles as a grouping. It'd be like if you called somebody a "tree". Sure, it may be a great insult, but you're applying their actions to a group they probably don't even belong to.
