:grouphug: I feel so bad for you and your son. I'm sorry you're going through this but I do believe you're asking too much.
Maybe it would help to look at it from the prospective of the other moms. As moms, we naturally protect our children and I believe the other moms are just protecting theirs. Imagine if a child in your homeschool group forgets that he should not eat x,y,z and goes to the play group, interacts with your son and your son has a fatal reaction. Now, imagine that child trying to live with the knowledge that his "thoughtlessness" caused the death of a friend.
That is too great a burden for any child to carry. I cannot allow my child to be placed in the position of carrying that burden. :grouphug: