I think parents of special needs kids need to be more understanding. (Kind of a SO)
For one......if your kid is making consistent noise over and over in public then it WILL annoy others. To YOU it may be nothing. Especially compared to how the child may act at other times. However to a parent with no SN experience it may not be nothing to them. It can be annoying and distracting.
2nd. People may NOT realize that your child is SN. Many SN kids do not look any different then a child who is not. To a parent who does not know you, all they could see is a child acting up in public and the parent not doing anything to try to stop it. YOU may know you can't stop him/her but others may not. Up until the last 5 years I had zero experience with SN kids. I would see a child acting up and never once did I think "hrmm maybe the child is special needs"
Lastly....you need to remember that you know a lot more about your SN child then anybody else. Getting an eye roll is not the end of the world. I know that a SNs child is NOT always controllable and so as parents you need to realize that sometimes your kids will annoy others (that goes for special needs or not). Learn to ignore the eye rolls or comments....but learn different ways to distract the child or remove them from the situation for a few minutes to cool down.