Ok - coming late here, but I'm am absolutely appalled that another parent sent you that! How completely classless! It's not like your child was caught plagerizing at Harvard. That is absolutely horrible. I'm so sorry you had to endure that. I wonder what the other parents and the teachers there would say if they knew about this? Isn't kindergarten supposed to be warm, fuzzy, and INCLUSIVE?
And you do have to feel for a child that is being brought up with a parent who thinks this way. Sad. Definitely sounds like a candidate for Springer.
Keep your head held high. It is really tough being stuck with that kid in your DS's class, but you did nothing wrong except be a good parent for your son. What a whack job. It makes my head want to explode thinking about it.