Honestly, as long as they don't put it in the spotlight, I think it should be ok. There are many animes that do it very tastefully. Cardcaptor Sakura for example. The problem is that Japan has a more accepting view of homosexuality where as half of the US do not. I was once contemplating this with MLP:FiM, but then realized that the main focus of the show is friendship and nothing more. Kids don't really have an interest in that sort of thing. Honestly, with the way it is now, it seems perfect. Give the kids what they want, and let more mature audiences form there own opinions from there. Take Lyra and Bon Bon. There's hardly anything that shows that they are a couple. Hell, there's hardly any time when the two are together, maybe only a couple frames. Take that and the fact that they're BG ponies and you don't really get a fleshed out character. Kids might see them as just more ponies, but we can take them and make them into whatever we want. As for RD, that's a little different. While I am a fan of the lesbian Rainbow Dash, there's not really anything they can do with her to express that without it detracting from the show or coming off as out-of-nowhere. They already expressed her character as it is. Now we should take it as we want. To little kids, they see somepony that like fast things and winning. To us, we many take it either way. As stated before, long-term relationships beyond normal friendship just isn't part of the show, even hetero ones. Rainbow Dash hooking up with Spitfire would come off just as awkward to me as any of the other main cast hooking up with a colt. Actually, I can see Rarity hooking up with some random colt after her issue with Prince Blueblood, but that's about it. But, with the main cast, aside from Rarity, they have already been fleshed out and seem to not even have any romantic interest at the moment. I feel just leave it the way it is for now and let the viewer take from it what they will.