I think sometimes people need to realize that your child is like 5, 6, 7 or even more years ahead of his peers. I think they are most threatened by the idea of a child 1 year advanced....being accelerated one year. There are too many kids that are one year advanced, and these rarely need acceleration! But many of these families assume you are taking your "extreme" actions for a similar situation, and this would be extreme. Once they "get" that your child is really unusual, I've found they typically turn more accepting.
I think that's a good point, Dottie. On those rare occasions when people see that DS6 is reading at the jr. high level and doing geometry, I can see their faces relax. It makes sense to them then that the standard school path without adaptation is not going to work well for him.
(And BTW, Cathy A. asked about a response for her grade-skipping child, so I think you're on task. It all amounts to much the same response anyway, since what people really want to know is "Why is your kid doing things differently from the norm?")
'Neato: I like the idea of "that's what works," but maybe more subtly stated?
