Clarity

They already treat them equally. There's no racism going on in the pony world. They'd have to change a whole lot if that was to happen.

Still, I think they should explain it, why Earth ponies aren't inferior to the other races.

Oh, but in Mare Do Well, Ponyville suddenly turned into a death trap, and in Putting Your Hoof Down, Ponyvillians became meaner. Don't they change quite a lot?