Yeah, I agree. AKR's main source of offense was in the name Derpy, which means (among other things) someone who is "slow." At least that was what her research turned up when she got those emails. She did say that she got 200 emails of praise for every 10 emails of vitriol, but those bad emails stung every time she saw one, much less opened it, because of her son. I should also make it clear that while she did get offended at it, it was Hasbro's decision to cut it in the end result. But I do feel for Amy, because if I had a son with that condition, I'd probably be a little sensitive to the issue, too.
I honestly prefer "clumsy" to "mentally retarded," because, well, that's just the feeling I got from the character. Her eyes being that way is a real medical condition, but the way she was voiced just made me love her to death because it just felt right for the character. Funny story: the "ditzy" voice that was used in the edited version is actually what Amy Rogers had in her head when she wrote the dialogue, and Tabitha St. Germain misinterpreted it as a boy's voice.