Calling autism a disorder is an accurate paychiatric description, not a value judgement designed to insult a person's identity. An insult can be targeted at a person's autism, but not simply by describing it according to clinical terminology.
I sympathize with people who don't believe autism should be considered a disorder, but that doesn't mean discussion needs to be encumbered by walking on eggshells. In particular, admonishing someone for using established clinical terminology is unproductive.