Who's Public Space?

Yesterday I was reading Rixa's children-in-public-spaces at Stand and Deliver and loved her eloquent take on something that seems to be a controversial topic lately after the original Feministe article and the response my-child-takes-up-spaceon Womanist Musings.  Do children belong in public space?  Are they/ their parents expected to maintain a particular code of conduct compatible with adult-only world?  And is it elitist and priviledged (and by extension "unfeminist") to suggest that adults have a right to quiet or child-free spaces?  I love the way Rixa summed it up: "How we treat children--our own as well as other people's--speaks volumes about our core values as a society. Children are our most vulnerable group, dependent on the adults around them. They deserve to be nurtured, loved, guided, and most of all, accepted as a normal part of what it means to be human."

I want to look at this from the perspective of special needs children who fit into both disadvantaged classes simultaneously.   My little man is more than 2, less than 3; thanks to fighting some serious medical disadvantages is not quite acting age appropriate in every way.  He does go out in public.  I consider him a person equally deserving of all experiences that are not dangerous to him.  We go to parks, parties, stores, etc..  He also sometimes has snacks when some might consider it a food-inappropriate moments.  Only in the last few months has he learned to start feeding orally.  I bring his favorite snacks and water bottle everywhere for every time he might feel like practicing his new skill. 
We still communicate pretty non-verbally and he does get frustrated and "temper tantrumish" when he can't express what he wants and sometimes this happens in public.  One day a month ago, we were out in the car and had no more Cheetohs left, which was a crisis.  We stopped at a grocery store and he excitedly walked all the way to the junk food aisle where we picked up the bag.  Then he freaked out and decided that I had to hold him.  I did not think that was necessary as he is perfectly capable of walking and needs a little encouragement to do more on his own.  I told him "If you walk to that aisle down there, I'll pick you up"  The whole way down, I'd walk a little in front of him and get him to come a few steps, carefully avoiding getting close enough for him to grab on and try to force me to pick him up. On the way, he was fussing (not disturbing anything at this big loud store.)  An employee made an acknowledging face at me and I laughed and said "he wants cheetohs!"  He said "I'm just glad its not mine.  I have a 3 yr old and 5 yr old"
I think he meant to convey understanding, but it still hit me the wrong way.  I wasn't upset or overwhelmed (though it happens on occasion.)  I've dreamed of the day that he would be alive and not on any drips or oxygen and walking in a public space and even expressed himself (even if by crying instead of actual dialog.)
I guess to me, the heart of the issue is this:  For any person, adult or child, that you may encounter, you really don't know.  You can't look and determine the chronological age of a kid and therefore what behaviors should be appropriate.  For any person, you cannot necessarily see superficially what their abilities are, the same way you cannot look at someone's race and know everything about their upbringing and culture.  Instead of running around being the "appropriate public behavior" police on each other, couldn't we all just promote a society of respect for all people that we encounter?  Can we learn to share this space?