I don't have a special needs child, and since being on Mumsnet I feel as if I have learnt a lot about people's feelings and reactions to this subject. It's also made me think a lot about my own behaviour and interactions with special needs children and parents.
I wouldn't necessarily assume you are being 'judged' (although I do understand why you might feel like that). I think sometimes people look on out of interest/ curiosity/ concern whatever - lots of reasons which are non-judgemental. I know I have done this in the past, but Mumsnet has made me realise it, and I now find myself 'checking' myself for doing/ saying something which might be construed as rude or judgemental.
Yes, people may be thinking 'why can't that mother control her child', but equally they could be thinking, 'gosh poor woman, she's got quite a lot to cope with' or 'that reminds me of my friend x's son' or 'I wonder how I would handle that' or any number of things.
I am also guilty of staring/ looking at mother's with twins and thinking, 'would I dress them the same or differently', 'how does she cope?' etc etc.
I'm not saying this very well, but perhaps try not to assume that if people are looking they are necessarily being judgemental. As a non-SN mum I find it very hard to know what the politically-correct thing is to say sometimes, and I am painfully aware of my own ignorance. Sometimes this manifests itself as a rude awkwardness or reluctance to engage. 