My oldest is in a wheelchair. I was shocked at what a difference that made. When he was still in his umbrella stroller, with a special seating insert, he was just the most adorable kiddo. Got comments all the time about how cute he was. The day he got his wheelchair, he became invisible. He was still absolutely adorable, my happy, smiling, flirty little boy, but that wheelchair was like an invisibility cloak. No one talked to him or made eye contact with him or me. I was shocked (and more than a little ticked off - I actually bought him a sweatshirt that said "Aren't my new wheels great?", LOL). But then I thought about it - I had avoided eye contact with- folks in wheelchairs or with- obvious disabilities up to that point. There was something about "disability" that made had me very uncomfortable, and I think it's pretty common in folks who have no personal experience with- it. It was eye-opening to be on the receiving end.
With difficult child, it was a little bit different because while his behaviors in public were seriously impaired, there was nothing that screamed "disability" so for the most part, he was just viewed as a rotten kid (and me as a lousy mom) in public. I think it would've been a bit easier if he'd had a horn growing out of his head or something - at least then, his "difference" would have been more easily identifiable for strangers.
Over the years, I've kind of adopted a three-pronged strategy for dealing with- public response. For the gawkers, I extinct them. They just aren't there to me. For the people who make cruel statements, I respond by talking to Boo (or difficult child when he was younger) and commenting on the statement (loudly). For the folks who initiate civil conversation, I explain what's going on. I think it's far better to educate when we can and try to break down some of that fear/discomfort of disabilities. While kids generally ran from difficult child (whirling dervish that he was, LOL), I do find that younger kids are more likely to come up and ask about Boo and his wheelchair (much to their parents' horror) - I love to take the opportunity to introduce them to Boo and explain about CP.
With difficult child, we certainly got our share of criticism from strangers (can't you control your kid?). I was probably less kind in those days, and would just bluntly state that my son was mentally ill and, while I was sorry to be disturbing them, I was doing the best I could.
I think we do become hyperaware of folks who look less than kindly at our children, and absolutely you are going to develop a thicker skin. It will wound your heart, probably always, but... you will kind of get used to it.