On the first encounter.
That's why they sent bicycle cops into a herd of angry WWII vets.
They we hoping that they would get killed or hurt so they could bring out the lethal weapons and sweep the area clean.
The essential flaw is that unlike their side, ours has manners and restraint. They simply couldn't imagine their sacrificial piggies would walk away unscathed.
Unfortunately, our restraint isn't unlimited.
The moral of an Aesop tale was that “A tyrant needs no excuse”.
But I like to point out that tyrants invariably generate excuses anyway. Hitler blamed the burning of the Reichstag on a couple of communists, who might have, but then again might not have.
In recent years there has been a disturbing trend among metropolitan police in cities hosting international meetings. Someone is telling them to break the law and rout protesters, with the idea of trading control now, in exchange for the eventual lawsuits later, with settlements paid out of taxpayer money. An interesting equation, if you think about it.
This throws the entire idea of peaceful protest out the window, with the public having to pay for the abuse of the public.
My point is that those in power are so impatient that they will wait around for an excuse to violently attack. When they order a violent attack it will be with overwhelming force against the most harmless of victims. If they can rout widows and orphans with pepper spray, it works for them, if not, they order the use of bullets.
So the focus needs to be on who is doing the abusing. In the recent shutdown it was the Department of the Interior, whose names are now at the head of the list for downsizing when next there is a Republican government. A strong lesson must be given to those who would oppress the public because they were “only following orders”, from anonymous political hacks.