Mr. Trump could expect that, since he was the host of the rally, he could deliver openly, unimpeded, his presentation. The demonstrators, having complied with the requirements for attendance by all other attendees,maintained their constitutional right to free expression but that right was fairly limited by Mr. Trumps' commercial control of the venue and by common courtesy. In other words, the demonstrators had no right to interrupt Mr. Tump's presentation and they had no right to prevent access to the presentation by the audience.
Mr. Trump nor his staff, however, had no right to physically interfere with the demonstrators as long as those demonstrators offered no physical imposition to other attendees.
Demonstrators who present physical impediments to the speaker or other attendees can be expected to comply with requests by the rally staff to leave.They may not, lawfully, be physically removed or attacked by anyone, except to avoid them causing damage to property or harm to others. If necessary, this is a job for municipal law enforcement.
If absolute restraint of opposing thought is allowed anywhere merely by the access to and expenditure of money, as in rental of a venue, buying of air time, payment for publishing, then 'free speech' becomes hostage to those with access to the greatest amount of funds, which we are already experiencing, to our pain and regret, in our government and our courts.
Beware.
It CAN happen again.