I’ve never been among those who equate mainstream advocates of a political philosophy with those on its radical fringe.

Just because someone is a committed liberal does not mean he or she endorses everything issuing from fever-swamp websites like MoveOn.org, or agrees with Robert Kennedy Jr. that those who question climate change are “treasonous” and ought to be prosecuted.

So I am initially inclined to agree with the view of left-wing MSNBC-TV host Melissa Harris-Perry, who complained recently that “right-wing media” were drawing a connection between the alleged crimes of Alton Nolen, accused of beheading a former coworker and stabbing another at a food processing plant in Oklahoma, and his conversion to Islam.

This, she said, was simply a case of “workplace violence” and the crime had no more relevance to his faith than what he had for breakfast that morning.

Well, OK, if what she means is that society should not impulsively conclude that everyone who converts to Islam is going to go on a gruesome killing spree. This was clearly the act of a deranged individual.

There is also no evidence that this was a terrorist attack – the most likely motive was revenge. An ironic aside: Harris-Perry and her guests made no mention, as most good liberals do, of how more gun control could have prevented this crime, perhaps because in this case the attack was committed with a knife, and stopped by a man with a gun.

But Harris-Perry’ case that Nolen’s Islamic beliefs are irrelevant gets weaker with a sober look at surrounding evidence.

On his Facebook page, Nolen called himself Yah’Keem Yisrael. He included images of Osama bin Laden, beheadings and fighters holding machine guns and other weapons. His former coworkers had complained of his efforts to convert them to Islam.

Nothing illegal about any of that – free speech is for everybody – although a workplace is not the place for religious proselytizing.

But what makes it significant – and undermines Harris-Perry entirely – is the left’s rampant inconsistency on such matters.

Just imagine – actually, you don’t have to imagine since things like this have happened and will continue to happen – that Nolen was a conservative Christian. Or Mormon. Or Jew.

Imagine that, as a recent convert to Christianity, he had been aggressively trying to convert coworkers to his faith, to the point where they complained of harassment.

Imagine that he had a Facebook page with images of God’s judgment on advocates of abortion and gay rights, with snippets of Old Testament verses of God calling for infidels to be “put to the sword.”

And then imagine that he had entered his former workplace and killed people in a fashion similar to that called for by Old Testament exhortations.

Harris-Perry and other talking heads on MSNBC would immediately draw a connection between his religious beliefs and his alleged crimes. They wouldn’t call it “workplace violence” and say a woman’s head simply “got severed,” which sounds more clinical than criminal. They would hold forth with outrage about how religious conservatives were inciting impressionable followers to violence.

Recall when John Salvi shot up a Planned Parenthood clinic in Brookline, Mass., in 1994. He was clearly unbalanced mentally, but liberal (and conservative) critics had no trouble concluding that religious leaders who taught that abortion is the murder of innocents motivated his actions.

This mentality extends to ludicrous generalities, as well. Since 9/11, I’ve been told by a number of my liberal critics that right-wing Christians are the “real” terrorists, simply for saying there is such a thing as right and wrong.

For some reason, they never provide any video of Christians shouting “Praise God,” as they fly jetliners into skyscrapers or slaughter innocent civilians by beheading, crucifixion, chemical weapons or simply mowing them down with machine guns if they refuse to convert.

Why the inconsistency? I think the most compelling evidence for those who downplay or dismiss altogether the religious roots of violence by Islamists is fear. It’s perfectly safe for them to mock and castigate Christians, Mormons and Jews, or to try to get them fired if they dare say anything in opposition to abortion or gay marriage. The chances of any kind of violent retribution are essentially nil.

Islam? Not so much.

The fear is rarely acknowledged, but it is there. Consider the hit Broadway musical “The Book of Mormon,” by Matt Stone and Trey Parker, creators of the crude “adult” animated sitcom “South Park.” I haven’t seen it, but my friends who have say it is uproariously funny while viciously mocking the Mormon religion.

So, I ask, when do you think they’ll write a similar musical called, “The Koran,” mocking Islam in a vicious but uproariously funny way?

They smile and chuckle a bit uneasily. Because, of course, if Stone and Parker want to stay alive, they will do no such thing. And that should tell you a lot of what you need to know about the difference between Islam and Mormonism. Or Christianity. Or Judaism.

Consider what MSNBC analysts would say if a fringe group of Christians insisted on the genital mutilation of women, on forbidding young girls from getting an education, or preventing women from voting or driving. The mockery and calls for prosecution would be endless.

So it’s fine if they want to argue that we shouldn’t tar all of Islam because of the actions of its radicals. But they should at least treat other religions the same.

Taylor Armerding is an independent columnist. Contact him at t.armerding@verizon.net