If you say to your enemy, "I won't help you say nasty things about me, and I won't permit you to say them on my property", that is completely within your rights

If you say to your enemy, "I won't help you say nasty things about me, and I won't permit you to say them on my property", that is completely within your rights. That is not censorship. It's only censorship if the government is doing it, and that's something we cannot allow - it's a violation of individual rights if the government prevents you from speaking your mind to a friend or using your property to communicate with many people.