I feel that those that got upset over Derpy's quirks werent able to see her for the pony she is, they just saw the negative aspects of her personality. I know that the team behind MLP: FiM wouldnt create a character to be offencive, but instead to be a role model. If an episode were made that showed all the positive aspects of Derpy, then maybe those who were offended before would see their mistake, and that Derpy is a wonderful pony, just like everyone else, just like their friends, family, or children are, regardless of a little derp in their step.