It's not multiculturalism with a small "m" that is the trouble. I have no problem with my children having black kids, jewish kids, all kinds of kids in their classes. I like that they hear liberal AND conservative ideas. I like that they are exposed to different religions and nationalities.
It's Multiculturalism that is the problem. When it becomes a holy grail to be achieved, rather than a natural result of different humans interacting, it's pc nonsense.