I understand the temptation -- really, I do -- but you can't go around punching Nazis, not unless they try to punch you first.

You also shouldn't make folk heroes out of people who do go around punching Nazis. And yes, by that I mean antifa. They are by no means friends of liberty or democracy, and in fact they endanger the very values that they profess to try to defend.

Before we go further, let's set some things straight, because it's complicated and clarity is essential:

1.) It has been argued that Donald Trump has tried to equate neo-Nazis and white supremacists with antifa.  That's not quite accurate. For whatever reason, Trump has been more emphatically critical, more specifically, of antifa than he has of white supremacists. Furthermore, the two groups are not moral mirrors of each other. Both wallow in violence, but one group endorses doctrines of racial superiority, genocide and hatred. One group does not. The difference in goals matters. A lot.

That said, liberals who treat Trump's criticism of antifa as evidence of the movement's value are in effect outsourcing their independent moral and political judgment to Trump. I'd be very wary of doing that.

2.) By multiple accounts (see here and here and here), antifa did do important, perhaps even life-saving work in Charlottesville, protecting peaceful counter-demonstrators and clergy against violence perpetrated by white-supremacist and neo-Nazi groups.

"They came to defend people, to put their bodies between these armed white supremacists and those of us who could not or would not fight," recalled Logan Rimel, a protester at Charlottesville committed to non-violence. "They protected a lot of people that day, including groups of clergy. My safety (and safety is relative in these situations) was dependent upon their willingness to commit violence. In effect, I outsourced the sin of my violence to them. I asked them to get their hands dirty so I could keep mine clean. Do you understand? They took that up for me, for the clergy they shielded, for those of us in danger."

3.) However, let's face the truth: The largely defensive role played by antifa at Charlottesville is not typical of the loosely affiliated groups that identify under that banner. It was the exception. In other parts of the country, in other incidents, antifa have been the clear aggressors. On multiple occasions they have physically attacked peaceful right-wing demonstrators. They have used violence and the threat of violence to bar right-wing speakers from college campuses, a direct violation of free speech to which all are entitled. In short, they have acted as anarchistic, violence-prone adrenaline junkies.

I've seen and read the excuses for such behavior. "They are fighting fascism," the argument goes. "They are employing violence to shut down hate speech and hate groups, and those are evils so great that violence against them is justified."

No. No, it isn't. Because once you've embraced that exception, all kinds of problems present themselves. If hate speech and hate groups are legitimate targets for violence, who gets to define "hate speech" and "hate groups"? Are you really comfortable with secret antifa cells getting to decide which groups will be allowed to participate in public debate, and which are not?

Are you willing to let other groups make that same kind of decision?

Some on the right see Black Lives Matter as a hate group. Others see Islam as a hate group. According to that notorious #AlphaFail, Sebastian Gorka, the Southern Poverty Law Center is "a racist hate group." In Portland, Ore., a local "rose parade" was canceled earlier this year because local antifa had threatened violence if the Republican Party was allowed to participate, and because antifa there had demonstrated the capacity to carry out the threat.

Again, no. That is not by any means acceptable. And these examples aren't the excesses of antifa. This is the essence of antifa. Endorsing antifa is the left-wing equivalent of endorsing "Second Amendment solutions," and it creates the same sort of problems.

You cannot use organized violence and physical intimidation as political tactics, as antifa does, and then claim to be anti-authoritarian. Political violence is the core of authoritarianism.