I don't think it's fair to assume that Duncan wrote what he did in an attempt to be malicious. It was a spontaneous moment and one that I don't really think was an ugly one. We of course can never know his true intent but shouldn't we give him the benefit of the doubt?
BTW, I'm a big Ms fan and my daughter has adopted them too (probably because she can't escape them) and she refuses to wear green because of the As. She's 9. I think we're selling kids short by suggesting "they're only in 5th grade".