Scientists have done all kinds of experiments to understand the mind and how we make decisions. One psychologist named Stanley Milgram performed a series of experiments to determine what percentage of the population was likely to remain obedient to authority, even when that authority was directing them to cause harm to another person. The inspiration for these experiments was one of the common defense arguments during the Nuremberg trials that they were "just following orders" and therefore shouldn't be held liable for their actions. This was not found to be a suitable defense, but it made Dr Milgram curious how likely the average person is to administer harm to others simply due to a directive given by an authority figure.
The experiment laid out the following scenario for test subjects. Subjects will be paired up with one being a "teacher" and the other filling the role of "learner". The student will be given a list of word associations which they are expected to memorize. When they are ready the student is moved to a separate room and hooked up to electrodes which are connected to a device that the teacher controls. The teacher will go over the list of words and administer incrementally more painful and potentially harmful shocks to the student each time the make a mistake. If you are unfamiliar with this experiment take a moment to come up with a hypothesis. What percentage of people do you think would be willing to harm others in compliance with perceived authoritative direction to do so? Well according to over 400 psychologists polled by Milgram at the time, the expectation was that little over 0.1% would actually be willing to execute the strongest shocks.
Unbeknownst to the test subjects, Milgram had conspirators who pretended to be subjects who were guaranteed the student position. No one was harmed during any of the original experiment or any of the variations he ran afterwards. The teacher would be given instructions on how to increase the voltage administered with each wrong answer, and he would proceed to read through the list while the student was intentionally providing incorrect answers. The original experiment took place in the 60s, but it's been repeated many times. Here is a short video of the experiment being reproduced in recent years.
What Stanley Milgram and his team discovered was that approximately 2/3 of participants were likely to perform the shocks to the full strength. Others have confirmed the experiment results all over the world. There do not appear to be any differences between men and women in the results. With the same parameters, this experiment has produced reliable results over the course of over half a century.
What this means is that given the parameters of the experiment, out of 3 people, 2 are likely to be willing to administer harm to others if an authority figure demands it. It's pretty scary to consider, but what I found most amazing was that in one of the variations they applied a "Social Support Condition" where they planted conspirators as teachers who would reject the experiment and push back against the authority within the view of other subjects. This has an amazing effect of helping others understand that rejection of the authority was an option, and this study showed that for every 10 people, only 1 was likely to comply. Knowing this, it makes sense that authoritarians would find it essential to remove speech that could usurp their control over the majority. Knowing this we understand why that speech is all the more important, and we understand why it's so important that we don't cede any more ground on 1st Amendment issues.