Facebook is enough of a utility / sticky service that banning free speech that is not clearly against TOS (and this is NOT a hate group!) is unethical.
Facebook is a website to post some crap on. There are thousands of such sites, they weren't granted a monopoly, and they didn't build infrastructure.
I'm all for freedom of speech, and I think that the picture of Mohammad day is a celebration of that, and not wrong (do not liken making fun of crazy people to racism, it's not the same thing, and the draw Mohammad day event is specifically a protest against violent reprisals towards those who expressed their freedom of speech). However, Facebook is not a public forum, it's not government property, and it's not a utility. It is a privately owned website, and they can remove whatever they damn well please.