What’s behind the recent spread of outraged mobs on US streets, wild-eyed and throwing violent fits because their favored political outcome didn’t happen? How did so many Americans give up on resolving disagreements through discussion and turn the fact that a disagreement exists into an excuse for a tantrum?

Campuses started setting up “safe spaces” well before 2015, when the news hit our media in earnest: College students were literally taking shelter from the possibility of hearing opinions they might disagree with.

For all the mockery the idea received, we’re seeing that principle extended to the real world. The recent outbursts on our streets have their root in the idea that only one opinion is the correct one and all others must be shut down.

And politicians are encouraging the idea that disagreement is a personal attack: “You cannot be civil with a political party that wants to destroy what you stand for, what you care about,” Hillary Clinton said last week.

“If you don’t agree, unfriend me” is a common enough post on Facebook — and that’s directed toward people who are supposed to be your friends.

It’s not a big leap from there to: If you don’t agree, you can’t have dinner, as Ted Cruz found out recently when he was chased from a restaurant. Or to yelling at Sen. Jeff Flake in an elevator. Or to: If you don’t agree, I can physically assault you, applied to strangers on the other side of your protest, as happened recently to the Republican son of President Barack Obama’s national security adviser Susan Rice.

We’re also years into those pre-Thanksgiving articles about how to talk to members of your own family who have a different political perspective. Most pieces now advise you to avoid talking politics altogether. That’s normal, actually — but if you avoid the subject because it makes you bristle with anger toward the people you love, that’s a problem.

It’s not just far-off relatives with a different political perspective that raise the ire of those unable to handle disagreement. In a Washington Post op-ed, “Thanks for not raping us, all you ‘good men.’ But it’s not enough,” Victoria Bissell Brown writes that she raged at her husband because of some small comment “I yelled at my husband last night. Not pick-up-your-socks yell. Not how-could-you-ignore-that-red-light yell. This was real yelling. This was 30 minutes of from-the-gut yelling.”

This is not normal. This is not behavior that should be rewarded with publication of an op-ed column on a non-fringe website. Bissell Brown is a retired history professor; the lessons of safe-space campus culture weren’t limited to students.

And when she reports that “I announced that I hate all men, and wish all men were dead,” that isn’t a joke we can all be in on. The inability to resolve conflict normally even in our own homes is exactly what spills out onto our streets.

After the 2016 election, we heard lots of admissions that many of us reside in political bubbles where we never hear outside opinions. For a while, it seemed like the consensus was that this was a negative thing. But now people increasingly retreat to these bubbles, proudly, and never learn how to handle political disagreement.

The result is the rage we’re seeing now. The more we shut off hearing the other side’s point of view, the more likely we are to see these mobs spring up.

Former Attorney General Eric Holder said last week, “Michelle [Obama] always says, you know, ‘When they go low, we go high.’ No. When they go low, we kick them. That’s what this new Democratic Party is about.”

Criticized for encouraging violence, he called it “fake outrage” and tweeted that he only meant “Republicans are undermining our democracy and Democrats need to be tough, proud and stand up for the values we believe in — the end.” He didn’t explain how his kicking comment made sense in that context.

When the other side is seeking to “destroy what you stand for,” or “undermine our democracy,” violence doesn’t seem so far-fetched.

In covering the early days of “safe spaces,” Conor Friedersdorf wrote for The Atlantic about student protesters who didn’t want a reporter filming them: “At various points, they intimidate him. Ultimately, they physically push him. But all the while, they are operating on the premise, or carrying on the pretense, that he is making them unsafe. It is as if they’ve weaponized the concept of ‘safe spaces.’ ”

Never learning to argue out their political beliefs, these people have graduated and now expect their opinions to always be shared and their favored political outcomes to always occur. Instead of being told to grow up, they’re encouraged to express their fury by people who should know better. Better for everyone if they had their rude awakening sooner rather than later.