A grim-faced President Trump offered the nation appropriate words of unity and deep concern this morning in the wake of an ambush attack on Republican congressmen at a ballfield in Alexandria, Va. The president also thanked those in the Capitol police who had risked their lives to bring the attack to the end, and offered prayers for the victims.

"We may have our differences, but we would do well in times like these to remember that everyone who serves in our nation's Capitol is here because above all, they love our country," the president said.

The gunman, identified as 66-year-old James "Tommy" Hodgkinson of Illinois, had been armed with an semi-automatic assault weapon of some sort, along with a pistol. He was eventually shot and killed. Four others, including House Majority Whip Steve Scalise and two Capitol guards, were wounded but are expected to survive.

Hodgkinson, who volunteered in the Bernie Sanders presidential campaign and later supported Jill Stein, apparently acted out of anti-Republican political animus. Based on his statements on social media and elsewhere, Hodgkinson saw Trump in particular as a traitor to his country.

Sanders made clear in passionate remarks on the Senate floor that he was "sickened by this despicable act."

"Violence of any kind is unacceptable in our society and I condemn this action in the strongest possible terms. Real change can only come about through nonviolent action, and anything else runs against our most deeply held American values," Sanders said.

Every day, of course, an average of 26 Americans are murdered with firearms, and mass killings have become much too familiar. Today's target was Republican congressmen. Tomorrow's may be schoolchildren, or black parishioners, or a gay nightclub, or college students, or concert-goers, or ... you get the point.

However, politically motivated violence poses a special type of threat because it is an attack not just on fellow human beings but on the system and process of government, on the community that holds us together. That's why the words of unity from President Trump, Senator Sanders and other top leaders across the political spectrum are so important. It's why the baseball game between congressional Republicans and Democrats must, and will, go on tomorrow night as scheduled.

Based on what we know, Hodgkinson attempted to impose through violence what he felt could no longer be obtained through debate, representative government and the ballot box. And that's the danger that is courted by some on both the left and right who like to tell us that the system is irretrievably broken, and who set out to ensure that it remains broken. As faith in the system recedes, violence can come to seem a more and more viable response.

As Sanders noted, that "runs against our most deeply held American values."

In another sense, though, Sanders is wrong. A strain of American thought popular in some quarters holds that political violence is not only an acceptable means of forcing change, but that the right to engage in that violence is protected in the Constitution. We need to deal with that as well.

By chance, one of those attacked on the ballfield this morning was U.S. Sen. Rand Paul of Kentucky. Here's what Paul tweeted almost exactly one year ago:

What happened Wednesday morning on that ballground in Alexandria was that noxious, destructive theory put into action.

Once you validate that theory, once you claim that Americans have an inherent right "to shoot at the government when it becomes tyrannical," you don't get to control who decides to exercise that right, or when, or who the target might be. Under that theory, individual citizens have a constitutional right to decide on their own when a government becomes tyrannical, and are acting legitimately and even patriotically if they turn to violence in response.

Well, hogwash, they don't have that right. Hodgkinson didn't have that right. Two-bit right-wing militia groups such as the sadly dangerous "III Percenters" here in Georgia don't have that right. Nor do they have the constitutional right to the type of high-powered weaponry needed to make armed attacks on government more effective.

Violence is not an acceptable response to political frustration, and no amount of romantic, vigilante-style claptrap can change that fact, regardless of where you stand on the political spectrum.