Actually, nothing happens if it's actually a majority group (as in, maintains a higher position of power than the given minority group prejudiced against it)
Were black slaves prejudiced toward their white owners? Probably. What happened? Jack shit.
Now if you have a so-called minority that actually can invert that power structure somehow (say, you're the one straight guy at an Imagine Dragons concert) then, yes, a group which is a minority in other contexts may exercise prejudice over members of the would-be majority. However, that doesn't often happen and to pretend otherwise makes you sound like a whiny ****.