Actually, it has everything to do with free speech. Here in the US, it is absolutely legal for me to say, for example:
"Those pig-fucking ape-brained Germans should be exterminated, each and every one. Everyone should find the nearest Germans, burn them out of their homes and shoot them down as they flee, men, women and children alike. And in the future, little children should be taught in school to celebrate the wholly righteous total genocide of the German people."
Because, you see, in the US I actually have freedom of speech.
Facebook policy, of course, bans such a statement just like it bans bare breasts, but US law doesn't require the censorship of either.