About this whole Derpy Hooves thing...
I didn't really feel like making a whole big post about it, but it is bothering me, so I at least wanted to write down my immediate thoughts.
In regards to the whole argument of ableism, I mean, I'm not gonna say that you're wrong. If you see the name and the character as offensive, you are perfectly entitled to your opinion. Goodness knows there's plenty of situations where what one person might intend or interpret as completely innocuous might be interpreted by another as being offensive - especially when it comes to the entertainment industry.
I personally do not believe the name to be offensive. The words "derp" or "derpy" in my mind is no different than the word "dumb". Can they be used in hurtful ways? Of course they can. Is that the intent of the word? I don't think so. A word is just a word until we attach an intent or context to it. The rumor is that they are considering reverting to Derpy's originally proposed name of "Ditzy", but is that any better? Her mane is yellow; should I rally against the creators of the show, then, for perpetuating the offensive "dumb blonde" stereotype? Her name was derived from both her personality and her distinctive wall-eyed look - so let's talk about those.
So what's in a name? Before Jan. 21st ("The Last Roundup"), Derpy's "official" name was intended to be "Ditzy Doo", as stated by Lauren Faust. Derpy was the name given by the fanbase because of her eyes, which resembled the Internet image meme of showing a person or animal with crossed or wall-eyes and the caption "herp derp" or "derp". In general Internet lexicon, "to derp" became slang meaning "to make a mistake" or (according to UrbanDictionary) "a simple, undefined reply when an ignorant comment or action is made". Assuming the original name of "Ditzy" (pre-"Last Roundup"), don't both of these descriptions still fit her background appearances quite well? She had been shown in scenes to be prone to making mistakes or inattention. The intent was, certainly, that she was a somewhat accident-prone and foolish pony. Regardless of whether her eyes were the result of an animation error or an intentional (presumed minor at the time) gag thrown in by an artist, the Internet community thought they were cute, and they ended up sticking. Again, speaking personally, I did not see any of the above as offensive. The bumbling sidekick is not an uncommon character type, and physical comedy is generally entertaining, especially for MLP's intended demographic of young children. For this reason, speaking strictly on personality, I don't think it's possible to interpret her character as offensive: there have always been bumbling, slapstick characters, especially in children's shows - mainly because they work for their demographic - and so to condemn her on personality alone would be to condemn a wide swath of characters that have not garnered this kind of attention.
So the personality is a character type that has been used before and largely has not been seen as offensive, and the name "Derpy" aptly describes this personality, and although it is a word that can potentially be used to belittle a person with a handicap, the intent isn't there in this case... that brings us to the eyes. Her trademark wall-eyed look was, to the best of my knowledge, not intended to be offensive, and was merely the result of either an animation error or an animator's little "easter egg", as I mentioned earlier. If we put all three together, though, some people seem to feel that it has become offensive. I can't imagine that people are reaching the conclusion that because this character is wall-eyed and clumsy, she is mentally handicapped. Based on my earlier reasoning, that seems like an awfully silly assumption.
What I can understand is the fear that children may see this character and assume that it's okay to laugh at someone who's "different". That could be true of so many characters, though, couldn't it? Isn't the part of the entire gist of the series that even though there are earth ponies and pegasi and unicorns (and a zebra! Her entire introductory episode was about not judging people who are different from you!), they all find a way to live with each other in harmony? That even though they have so many differences, they enrich each others' lives and see the pony (or person) underneath, and offer them their friendship?
No pony has ever called this pony "derpy" (or "dumb" or "stupid" or anything) out of hatred or disgust or anything of the sort. She's been chastised for making mistakes, but shoot, I'm pretty darn clumsy myself, and I've made plenty of mistakes and I'm not handicapped. Out of her personality and name, I honestly can't perceive any offense or sense of ableism with her character. With regards to her eyes: if you want to view them from an in-universe standpoint of them being indicative of some kind of visual handicap, I will concede. To take it as a whole with her personality and attempt to label it as a mental handicap: that I will disagree with. That is a label that you, as a viewer, are applying. I do not see it that way. And again, even if her eyes are indicative of some sort of visual handicap... is offense being taken because handicapped characters can't be slapstick characters? The difference here is in laughing at someone versus laughing at their antics. If you're worried that a child might not understand the difference, that is a valid concern - but given the overall themes of the show, it seems pretty clear to me that the intent was never to laugh at a character because of their differences. The show goes out of its way to stress that you should never make assumptions about or speak ill of someone just because they're "different".
I feel like either no one will read this post, or a bunch of folks will read it and start sending me angry comments about how I just don't "get it". But that is fine; I don't have a problem with that! These are just my thoughts on the whole thing, and I wanted to get them down. Please know that if anything I said came off as mean or insensitive, it was certainly not intended that way! If you disagree(d) with me, and you actually stuck with me and read through my reasoning for feeling differently, I deeply appreciate you hearing me out.