You're right, it's an emotional distinction. Let me illustrate. A man operates a gay rights message board that includes private messages. He tolerates alternate viewpoints, but after a particularly bad flamefest he uses a plugin to ban linking to a hate speech site that is especially contrary to the aims of the forum that he pays for out of his own pocket. It extends to PMs. He explains that if you want to trade such links you're welcome to go elsewhere.

Reasonable?