The first amendment has been evaluated by the supreme court on numerous occasion in the last 75 years. It has evolved in its interpretation as to what free speech really means and what limits free speech bears. Obviously if McCain rented the property, she could be asked to leave, and failure to leave could result in arrest for trespassing. But would she have a right to protest under any circumstance?

NO, because time PLACE and manner are all very important. There are limits to when where and how you can say just about anything. I can say obscene things all I want in my home, but saying them in a public place would lead to my arrest. In this case her protest put her in close proximity to those she protest against. If I were mccain and trying to avoid a lawsuit because someone at my event assaulted a protester, I would certainly remove the protester. Abortion clinics are open to the public but your conduct must comply with the wishes of the property owner, ie you can't take your dead baby sign into the lobby.

If this were city property that was rented out to a private interest (which it was, read the link above to the news article) those same rules apply. The city is certainly entitled to rent out property to private groups. And those groups can selectively choose who may enter them. For example, I could rent that same location and make "white males only" as a requirement for attendance. There is nothing illegal about that. Racist sexist and immoral, but not illegal. Do you find it odd that they brought a video camera to record the expulsion from the event? I don't, they knew in advance they would be asked to leave this event. Do you generally go to events designed for people you disagree with and not expect conflict?

I haven't seen the KKK at any Obama rally's, for a similar reason I would guess. I am definitely not a klan member, but It would be interesting to put on the garb and record what happened to me when I went to the rally. I could make an internet video and create a buzz about how the communist liberals don't respect my rights and completely ignore the fact it was a private event with conditional requirement for attendance. It would be similar to this video I expect with the exception the posts would be about communist instead of fascist.