I have read thru this thread with interest - I have a friend with a son who is mildly autistic, and another with a daughter who has severe disabilities from brain damage.
While I agree that parents of special children should not be judged, but those making the inappropriate comments should not be judged too, too harshly either. Comments like the "perfect parents club" are harsh and judgemental too. I don't mean to single out the poster who used that phrase - it's just the one that came to mind, but there are quite a few others in this thread as well. Put simply, no one really knows why another acts the way he or she does.
We each learn from our experiences. I personally could not understand how someone could lose a child - until I had my SECOND child. I learned from experience how different children can be. (And fast

)
My point is, those making the comments or rolling their eyes might have their own learning disabilities, past experiences, or other reasons for their behavior. Including, sometimes, lack of manners or ignorance. But you don't know that either. Just because someone appears to be a "normal" adult doesn't mean he or she is. My first husband was an alcoholic, and a mean drunk. But half of our friends were amazed when I told them the reason for our divorce, because they had never seen him drunk! Much like your son, you couldn't tell by looking that he had a problem.
To the OP, if you keep that in mind, perhaps it will be a little easier to let the looks and comments roll off your back, rather than making you cry. React to them the way you wish they would react to you and your child, instead of letting them take a bit of your power away from you. If you do not accept the idea that they are qualified to judge you, then the judgement becomes meaningless.
That being said, I do thank the heavens that I have two healthy normal boys - I don't believe I could have handled the trials and tribulations of having a "special" child and am in awe and admiration of those who do. I do believe you are special parents with more patience, understanding and stamina than I have - even if I don't immediately recognize you when I see you.