Actually, John, a perfect example of this guarantee would be Charlottesville itself. Jason Kessler set that rally up months ago, getting a permit etc... A couple of days before the rally was to take place Charlottesville pulled his permit for the park, citing public safety concerns. Kessler sued them, and a federal judge sided with him, granting an emergency injunction, ruling that it would violate his guaranteed right to free speech. From that point on it was the city's responsibility.
If people in this country still respected the Constitution the way they used to, and everyone took the same measures that they used to take to protect all speech at all costs, then the police would have been allowed to actually do their jobs and Antifa would have never gotten anywhere near the white supremacists. Those idiots would have spewed their hateful crap, then packed up and went home. End of rally.
Yeah, there may have been some property damage, a few side scrums, whatever, but the two sides definitely wouldn't have had free rein to go to war, there definitely wouldn't have been the same level of violence that was on display, and that young lady would more than likely still be alive.