It isn't that I don't appreciate the sentiment; I do. But fast on the heels of that affirmation are the misgivings: does this person really know me? Do they not see what it's really like, who I really am? And yes, having Asperger's or any other autism spectrum disorder is not, contrary to what PC people say (persons with autism, blech) separable from the rest of the person...sort of like your gender and race. Nobody refers to a man as a "person with maleness", to a gay person as "a person with homosexual attraction" or to my grandmother as "a person with Filipino genetic material". There is a reason that ASDs are called "pervasive" (although that doesn't sound like the kindest descriptor to me). When you are on the autism spectrum, it is not something you "have", it is an integral part of you that permeates every aspect of your identity. This isn't to say that the other extreme, autism as who you are, as the sole characteristic, is correct either. Of course any person on the spectrum has many, many other attributes, defining characteristics, and elements to their identity.
Another facet of this "you are normal, there is nothing wrong with you, society is what's wrong" (I agree with the latter statement by the way) point of view is that it seems to imply that if one cannot cope/perform/work/interact as competently as other people, it is due to a lack of trying hard enough...and I emphatically reject that idea. I've never met anyone on the spectrum who wasn't doing their damnedest to cope, who wasn't put under extra stress due to the strain and effort of trying to keep up. Nobody would say that an amputee was just as normal as a group of biped hikers and that if he/she couldn't keep up, it was due to not trying hard enough...but when you are on the spectrum this happens almost every day.
And that's just the ASD stuff. Most of us have at least one "comorbid" (what an ugly sounding word!) condition, such as depression, anxiety, PTSD, ADHD, Tourettes, etc. Having an anxiety attack is not normal. Having anxiety attacks regularly, when you are trying to get other stuff done, at work or elsewhere, is not normal...and being told that there's nothing wrong with this leaves one feeling somewhat lonely and alienated....as if they don't know who are are not because you haven't told them, but because they refuse to acknowledge that this is something you have to deal with, that it's something that can be a problem.
The sucky thing is, I really think that people mean well when they say this stuff. It doesn't seem to be said out of malice or insensitivity.