The university’s response was likely the quickest show of police force in response to a divestment protest among the dozens nationwide that have occurred in recent weeks. It was also probably the only one where pepper balls, stun guns and rubber bullets were used against students, faculty and community members – at one of the few student protests in the south to date.
For public entities, the protest can be considered unlawful and not violating rights by the bad actions of individuals which then causes police intervention, which then riles the crowd, and then it snowballs from there. Once the crowd is considered riotous, the whole thing becomes unlawful assembly. We saw this in Portland and Seattle years ago.
All it takes is one person committing assault or battery on another person and then the cops have writ to act as they see fit, this includes throwing a waterbottle at a cop that is full or empty or shoving someone. There is no real chance that any level of lawful police action will maintain the peace when you have groups of energized unhappy people. Just having police there agitates the crowd, not having police there allows bad actors to undermine the protest/peace and that leads to the police showing up.
If everybody protesting stood 6 ft apart holding signs in silence and did not react to agitators, they could keep protesting so long as no other laws prohibited it(like curfew). Unfortunately there are always idiots in any group and someone is going to overstep the line and cause the whole thing to devolve into chaos fuled by lawful police action.
SCOTUS has specifically rejected that argument. As at that point all you’d need is one infiltrator to shut down any protest.