I can sympathise here. My son is 6 but the size of a 8-9 year old and is diagnosed with classic autism and I sometimes think it would be easier if his disability was visual.
My son goes to a mainstream school and I take every opportunity i can to get him interacting with his peers in a controlled environment, so when after school football club came up I jumped at the chance. However, the teaching assistant who supervises the kids while they get changed is a real battle axe and I really dislike her (she helps out in my sons class a lot). So here I was standing outside the class with all the other parents while the kids got changed and I heard all the kids laughing. Next thing I know she comes out and tells me that my son had pulled his penis out through the slit in the front of his boxers in front of the rest of the kids
...she was quite clearly disgusted by this, so i went in to see to it and my son had already gotten dressed by this point. I asked my son why he had done such a thing and he replied that there's a hole in his boxers at the front and thats what its meant for, he was just checking it worked (he had not long started wearing boxers shorts)... I felt that (for a child with ASD) this was a fair comment to make and i could see his logic behind it, even if it was "socially" wrong. I tried to explain to him that he couldn't do that etc etc but the teaching assistant was clearly very annoyed by it and went on about how disgusting it was, and he'd not get to go to football lessons if he done it again etc etc .... she really upset my son. i was very close to making a complaint about her but knowing the head teacher she would have had the same attitude as the teaching assistant so I decided complaining would get me no where.
i have had several situations where my son has done things like, answered the door naked, went to play on his trampoline naked etc, he has really difficulties with clothes as he has sensory hypersensitiveness and so takes them off as soon as he feels he can, unfortunately he doesn't always get it right and sometimes we end up with him semi naked in others peoples houses (usually he'll go to the toilet and come out with nothing but a t-shirt on) etc, some people don't mind and take no notice and other people react as though they have a 26 year old walking through their house naked. Don't get me wrong, my son has to learn at some point that he can't strip off and wander about naked but some peoples reactions are just a bit OTT. We have started insisting that he wears at least boxers and a t-shirt when we have visitors in our house too and we have noticed that he is becoming a little more aware recently. He asked my best friend, who is used to the way he is, to not look at him while he was getting changed into his jammies... its a step in the right direction i think??
For me, the reaction of a complete stranger doesn't upset me, they don't know, they don't understand and they don't know how wonderful my little boy is or the struggles/achievements he has on a daily basis. The people who really upset me is the people who DO know but don't care to try understand, the people that know my son and his struggles and the people who know and understand about ASD but still expect him to be "normal". When they judge him it makes me really furious and I have actually cut a couple of family members out of my life as they were making a habit of it.
People are just ignorant, they don't understand how their ignorance can really upset and isolate a family who has a child with special needs. Its not easy at first but I have eventually learned to take no notice of those who don't know or are simply ignorant/judgemental.