"[P]oliticians like Mr. Trump who stoke anger and fear in their supporters provoke a surge of stress hormones, like cortisol and norepinephrine, and engage the amygdala..."

"... the brain center for threat.... This makes it hard for people to dial down their emotions and think before they act. Mr. Trump has managed to convince his supporters that America is the victim and that we face an existential threat from imagined dangers like the migrant caravan and the 'fake, fake disgusting news.'...  Just about any of us could be susceptible [to becoming violent] under the right conditions.... A 2011 study by Dr. Fiske and a colleague looked at 'social cognition' — the ability to put oneself in someone else’s place and recognize 'the other as a human being subject to moral treatment.' Subjects in the study were found to be so unempathetic toward drug addicts and homeless people that they found it difficult to imagine how those people thought or felt. Using brain M.R.I., researchers showed that images of members of dehumanized groups failed to activate brain regions implicated in normal social cognition and instead activated the subjects’ insula, a region implicated in feelings of disgust. As Dr. Fiske has written, 'Both science and history suggest that people will nurture and act on their prejudices in the worst ways when these people are put under stress, pressured by peers, or receive approval from authority figures to do so.' So when someone like President Trump dehumanizes his adversaries, he could be putting them beyond the reach of empathy, stripping them of moral protection and making it easier to harm them."

From "The Neuroscience of Hate Speech/Humans are social creatures who are easily influenced by the anger and rage that are everywhere these days" by the psychiatry professor Richard A. Friedman (NYT).

Here's one of the more interesting comments at the link:

Missing: women, 51%, are missing from this analysis and from the famous Stanley Milgram experiment reported. In fact women do not respond to violence in the same way, or to commands from authority figures as do men.

Women are not mass murderers in general and do not respond well to Trump. When speaking of violence generalizations like “Humans are social creatures...influenced by violence and rage” women are ignored.

Of course, no group "in general" is composed of mass murderers, and some women do respond well to Trump, and I don't really know if it's true that the brain studies have concentrated on men. When we worry about violence, we think almost entirely about men becoming violent, but the subject of angry and hateful public discourse relates not merely to who will be incited actually to commit violence. The main concern — let's face it — is how people will vote. If we are afraid of violence and become more vigilant, we're all very unlikely to commit acts of violence. But it becomes part of what determines our vote, and the most likely outcome is that we will just vote for someone like Trump who seems willing and able to protect us from violence.