Yep, some people are petty and mean.

I'll add that some people are so unnerved by difference of any kind that their only recourse is bullying. They may perceive themselves as "nice" and see the child as odd, deliberately nonconformist, or anything in Pemb's list-- which in their twisted minds may justify their cruelty.

What your DS will learn from this is to know cruelty when he sees it. I'm so sorry this has happened...