deal with a little boy who keeps saying mean things about Polly, now that she has three legs?

I've tried disagreeing nicely, but it's not working. Is he projecting? Why would a kid have a reaction like this? I realize I can't know for certain, but should I keep countering his comments, or ignore him?

For the record, Polly is an insanely sweet dog who loves everyone. Most people love her. He says nothing about her breed, just her "condition."

I'm flummoxed.

http://geaugadoggy.wordpress.com