To hold an event on campus, you have to be sponsored by an organization on campus.
However, no organization on campus wants those people on their campus.
Yes, I think the point he was making was the potential for a double standard - if a hate group / violent group associated with the left wing of politics were planning the rally they may not have blocked it even without an invitation.
I stand by my statement. If one of the sacred cows that I named wanted to rally, demonstrate or march tomorrow, no one would stop them. Hitler disbanded all the opposition political parties in one of his first moves as chancellor. How is that different from not allowing one side to rally here?