Fluttershy may be my favorite of the "mane six," but I have a soft spot for Derpy as well. I love how she's become a fully-fledged side character when she was originally just a simple animation error/light-hearted animator's prank. I felt the adoption of her fan name and speaking role was the best kind of shout-out a show like this could give. It was the ultimate inside joke for those of us in the know, yet the scene could still be appreciated at face value for the uninitiated.
Clearly, I did not account for the uptight, overly PC-obsessed crowd looking for excuses to be "offended."
Derpy has never been viewed as mentally disabled. She's merely a klutz, plain and simple. Lord knows there have been plenty of characters like her in other cartoons (Patrick Starfish, Heifer Wolf, Odie, Shaggy, etc.), yet nobody seemed to complain about them. Even if it was revealed that she was mentally handicapped, that wouldn't prevent the fans from loving her. How could we dislike such an innocent and likeable character, particularly when she's become our unofficial mascot? If anything, I'd say it's the detractors that are at fault here for trying to create controversy where there was none.
Come to think of it, I wonder if some of the "outcry" is actually the work of trolls trying to cause mischief. Some MLP haters go to absurd lengths to try and shut the show down, even going so far as pretending to be Hasbro so they can remove any and all related videos on Youtube (including fan creations).
It's good to see that Hasbro has apparently taken the high ground and decided to keep the name.