If the writing becomes trash, not if they change the direction of the show a bit. I mean if they have good writing, than the show will get away with a lot of things that people would say oh hell no to if they just saw it on paper.
I know I wouldn't treat someone worse because of something like pink hair. If there is one good thing about me being a social outcast, it's I'm open to being friends or getting to know anyone if we have similar interests. The person may get bullied by others but who knows for sure.
Sadly, I'm pretty ignorant to most cultures, so I just assumed they where all American. I guess they could be anything really, except maybe AppleJack with that think southern accent.
MLP isn't a shounen battle manga. There is no real power balance so you shouldn't have the characters battle one another. Also, why would you have an alicorn fight an earth pony.