Why exactly? You _are_ free from consequences .. from the government. But how would you expect to be free from consequences when you offend millions of people using the Internet? Why should I not be able to ban people from my forum if I and most of my users don't like them and they are dragging down the quality of the forum?

Those are consequences, and I don't see how you can have some utopia where that isn't viable. Then you just live in a world where you are forced to listen to the broadcasted thoughts of idiots.