Law Dog, you miss an essential point: the talk was open to the public. That means it's a public event. Doesn't matter who sponsored it. You make a decision to open it to the public, you don't have a right to interfere with anyone's First Amendment rights.
So, you are arguing that once a entity opens to the public, they cede all rights and control to the public?
In other words, if a restaurant -- open to the public -- decides they have the right to refuse service to anyone, you would disagree?
Wal-Mart is "open to the public" but if someone starts raising Cain and acting a total oik, Wal-Mart doesn't have the right to kick them out anymore? Is that what you're saying?
If you decide to sell your house, and in doing so, you have an "Open House" to show off the architecture -- Open House being just that, your house is "open to the public" -- your argument is that you no longer can interfere? If someone decides they don't want to leave, you can't throw them out -- because your house was "open to the public"? If someone decides they want to sing all seventy squillion verses of "Henry the Eighth, I am, I am" at the top of their lungs, you can't make them stop -- because your house was "open to the public" and you can no longer interfere with his First Amendment rights?
Rights, I believe, we already established limit the government -- not private citizens?
Are you sure you want to take this tack?
If you decide to open anything to the public, you can decide to close it to the public. Or to any part of the public you see fit. At any time.
I say again, If I pay the piper, I bloody well get to call the dance -- I don't care who is there, I don't care if the entire bloody public is there: they didn't pay for it -- I did.
Stores, restaurants, theatres and every other privately owned business are all "open to the public", yet all maintain the right to refuse service to anyone.
Or are you arguing that they do not, in fact, have that right?