Words matter. Especially when they incite domestic terrorism.

Yes, words matter.

Vitriol aimed at Muslim refugees this month was followed by attacks on mosques. Dismissing the #BlackLivesMatter movement gave way to open gunfire on protesters in Minneapolis.

The flaming hatred of Planned Parenthood set the stage for another act of domestic terrorism Friday at a clinic in Colorado Springs.

Robert Lewis Dear Jr., a 57-year-old drifter with an extremist agenda, used the phrase “no more baby parts” after he allegedly killed three people — a police officer, an Iraq war veteran and a mother of two — and injured nine others in the rampage at the Planned Parenthood clinic. Grandstanding members of Congress fed him this line after the release of heavily edited video clips of a Planned Parenthood executive talking in graphic language about the donation of tissue from aborted fetuses.

Never mind that fetal tissue has been used in important medical research since the 1930s (helping produce vaccines for polio, measles and mumps) and has been funded by the federal government for most of those eight decades. And never mind that Planned Parenthood, a group that provides 2.7 million American women with contraceptives, breast exams and, yes, abortions, makes no money from the legal donation of fetal organs to medical labs.

Conservative lawmakers went wild, vowing to defund Planned Parenthood, holding hearings and turning the whole affair into a series of sound bites that boiled down to talk of “baby parts.”

Predictably, threats skyrocketed after the release of the tapes. Someone even posted a $10,000 cash reward on Fox Nation’s website for the execution of the Planned Parenthood doctor in the video. Which brings us to what just happened in Colorado Springs.

“Although antiabortion groups may condemn this type of violence when it happens, the way that they target and demonize providers contributes to a culture where some feel it is justifiable to murder doctors simply because they provide women with the abortion care they need,” said Vicki Saporta, president and chief executive of the National Abortion Federation.

She rattled off the numbers: Since 1977, there have been 186 abortion-related arsons, 42 bombings, 17 attempted murders and eight murders, including the 2009 killing of late-term abortion provider George Tiller at his church in Wichita, Kansas.

Yet some politicians don’t seem to care about the violence that their rhetoric helps incite.

Even as the standoff between Dear and police in Colorado Springs was underway, Rep. Adam Kinzinger, R-Ill., was shrilling on live TV, slamming Planned Parenthood while a gunman was still inside the clinic.

It was barely over before the ugliest people in the antiabortion crowd went on social media to cheer the deaths, calling the shooter a “brave hero” or saying that any woman who was there for an abortion that day and who was killed “deserved it.”

This is what terrorism looks like. Leaders incite and inflame with fiery speeches and threatening words. They cite heavily edited propaganda videos. They use violent language. And they unleash the worst impulses of the unstable and the unmoored.

That may not be their intent. But for those folks predisposed to aggression, violent speech increases support for violent actions, according to a 2010 study by Nathan Kalmoe, an assistant professor at the University of Michigan.

“The results presented here clearly refute the claim that violent political rhetoric is without negative consequences,” Kalmoe said. “The evidence might be sufficient to make political leaders think twice before infusing violent language into speeches and ads, particularly in situations when their audiences are already boiling over with hostility.”

It was only a few years ago that we had this debate after former Republican vice presidential candidate Sarah Palin posted a map with crosshairs over members of Congress she wanted out of office and tweeted, “Don’t retreat, RELOAD!” And when then-Rep. Gabrielle Giffords, D-Ariz., one of the people in Palin’s crosshairs, had her office vandalized, she asked folks to tone down the rhetoric. Soon after, in 2011, Giffords and 20 other people were shot — including six fatally — outside a Tucson supermarket.

For months now, opponents have been defacing signs supporting the #BlackLivesMatter movement. And politicians, Democrats and Republicans, have tried to neuter the movement by declaring that “All Lives Matter.”

It didn’t take long for the hate to escalate to the shooting of five people outside a police precinct who were protesting the killing of a black man in Minneapolis. Fortunately, no one was killed.

The nation is finally examining the lethal police tactics that have cost the lives of too many unarmed black men and boys. But hostile anti-police rhetoric — including protesters shouting for “dead cops” — helped fuel brutal, execution-style murders of police officers in New York last year and Texas this summer.

The same overt hate is being aimed at American Muslims, since the Nov. 13 terrorist attacks in Paris.

There have been outrageous proposals to shut down mosques, register American Muslims and reject Syrian refugees who are not Christian. The result?

A taxi driver in Pittsburgh was shot in the back on Thanksgiving by a passenger who confronted him about his country of origin and who then began ranting about the Islamic State group. People armed with weapons surrounded a mosque in Texas, then offered a list of home addresses for those who worship at the mosque. A fake bomb was dropped off at another mosque in Falls Church. Neighbors turned on one another in Fredericksburg, Va., where a mosque that has been in town for almost three decades was decried at a community meeting. A man who has lived side by side with these people for decades stood up and yelled, “You’re all terrorists.”

But the vast majority of terrorists in this country aren’t Muslim. They’re white men who were born here and have utterly changed our daily lives with their anger-fueled rampages.

No place is safe from them anymore: not schools, not offices, not movie theaters, not malls.

Yes, mental health is an issue. Yes, easy access to guns is an issue. But words are an issue, too. And toning down hateful rhetoric would be an easy place for everyone to begin finding common ground.