All fandoms are legit, as long as they have fans! There is no question that MLP has lots of fans. It certainly overlaps with furry, just as almost every other fandom in the world does. Fur example, I'm a fan of sci-fi, plushies, Disney, funny music, and I'm also a furry. To me, these things are all related, even if it is only because they are all a part of who I am. To someone else, there might not be any connection at all. That's the way it is with people in the MLP and the furry fandoms. Some are in both, and the fandoms overlap to the degree that it's nearly all one thing to them. Others make no connection at all, and some actually hate the fandom that they are not a part of, for one reason or another.

As for me, I'm not a fan of MLP, but I like enough about it to be an appreciator of it. I might even like it more if I had cable TV and the time to devote to watching it, but I don't. It does produce sort great art from time to time, despite me not knowing an Applejack from a Dash, or whatever. It's as legit as furry, and that's coming from a furry cub raccoon who wear shortalls, so it must mean something! :)