It's also worth mentioning that Regular Show is TV-PG, while My Little Pony: Friendship is Magic is TV-Y7. I can't think of a single moment in this show that was so intense that it warranted swearing, or any jokes that would have needed profanity to be funny. So, no, I don't think they should include profanity in shows that are aimed for a younger audience such as My Little Pony. It's just not necessary, and I don't think the "they'll end up learning the words anyway" excuse should be used to justify stronger language.
I understand that many kids and teenagers swear very often (I personally don't; at least, not out loud), but it wouldn't hurt to try and reduce that number, and having profanity in My Little Pony wouldn't help that.