Why would anyone even care about Derpy being changed?
She's not even that interesting of a character anyways.
the first fans found her, gave her the name, and she basically just became the icon of the fandom over time. everyone on the show's crew knew who she was, Lauren Fast knew, the current director knows, the artists/musicians/voice actors/ know, and so on.
she got some real airtime for the first time, was actually called Derpy by one of the characters (Rainbow Dash), and now the episode in which this took place was changed to remove that.
A long time fan favorite got to be part of the show for a quick minute, this pleased many viewers, but then they took it away for an unknown reason. It makes sense that those who know and enjoy Derpy would get a little on edge because of the situation.