She's right, and society has known this since the National Socialists committed the Holocaust, but people like to cite the Milligram Experiment.

People don't realize that the Milligram Experiment wasn't just one group of tests with a guy in a lab coat. That was only the most effective way of getting people to comply with authority and commit acts of violence against their conscience: project an air of authority and inevitability, without ever assigning responsibility. "The test must continue"

When the fake experimenter didn't wear a lab coat, or told the patients to flip the next switch, they had less compliance. The absolute worst test outcome was when the fake experimenter explicitly ordered the participant to flip the next switch.

The reason these experiments were tested like this is because the National Socialists ran into the same problem early on in the Holocaust. They found that they were actually taking massive rates of attrition from their death squads. Even though these were heavily propagandized, ideologically possessed, Hitler worshiping, zealots; within a week or two: they'd be broken men. You can only personally witness so many deaths within such a short frame that it breaks people. They literally started testing and documenting ways with how to keep the killings going, and they found (just as Milligram did), ordering the executioners to keep shooting people, even at the risk of themselves being shot, gave them the worst responses, and the most derelictions. Again, the solution was: inevitability, devolution of responsibility, and presentation of authority. They gave pep talks. This increased the length of time that the executioners could last, but it still wasn't very long. The more death each person witnessed, the worse it effected the minds.

This is actually the basis for why they needed gas-chambers, dedicated execution facilities, Sonder-Kommandos to do most of the gruesome work, and why the officers and permanent staff got very nice accommodations: a desperate need to preserve morale.

A lot of the same lessons work here. Start with voluntary compliance and an effort to see it as an inevitable action that is being explained (not ordered) by authority figures. That gets the most results. Follow it up with incentives, and you're going to have the majority of the population complying with you. Then, you balkanize the rest to solidify your political control over the people that complied, and to ostracize and justify limitless violence on those that didn't.