Racial, I'd say, because of the genetic difference.  (Of course, the same could be said of hereditary deafness, but autism isn't necessarily disabling.)

It's another category that society uses to justify throwing away people who are different.      I wouldn't use the word "retarded" to describe anyone because I don't believe a person can be reduced to a number on a test.

Many people didn't want to reject the word Negro in favor of Black or African-American because they looked at the issue that way.

As I see it, there isn't any shame or self-rejection involved in dumping that ugly old historical baggage.  Rather, it's a positive assertion of the right to define oneself.