People who would otherwise post on Facebook about Holocaust denial can go out on the streets and talk about it to their friends or others. But, they can expect a punch in the face if they do. I think that is what is happening here. People are spewing nonsense, and a non-governmental entity (Facebook) is punching them in the face (not letting them say it on their platform).
Like the grandparent post said, this is intolerant. But it's following the paradox to allow more tolerance in society.