Amendment I states,
Congress shall make no law...abridging the freedom of speech, or of the press;
The key word is "Congress." And since the ratification of Amendment XIV, state and local government as well.
With that being the case, private property owners have no constitutional or legal obligation to let any one speak or for that matter to speak about any topic.
I think you miss the point. Dease is saying that Coulter should not be allowed to say what she said. That is anti-free speech. If Dease had simply disagreed with what Coulter said, THAT would be free speech.