Only a fool believes that all those with whom he differs are bad people. Moreover, just about all of us live the reality -- often within our own family -- of knowing good and loving people with whom we strongly differ on political, religious, social and economic issues.

That said, I have come to believe that the more committed one is to leftism, the more likely one is to become meaner.

Two examples in just the past week offer compelling evidence.

Prominent left-wing commentators used the way in which Rick Santorum and his wife handled the death of one of their children to attack -- make that mock -- the former Pennsylvania senator.

In a lifetime of observing and participating in political debate, I have seen a lot of meanness. But one just assumes that some things -- not many, just some -- are off limits to political pundits and activists.

Among these few things, one has to believe, is the death of a child.

But I was wrong.

In 1996, Karen Santorum gave birth to a premature baby boy who died two hours later. After spending the night in the hospital with their baby son between them, the grieving parents brought the lifeless infant home for a brief period because, Santorum explained, it was important to them for their other children to "know they had a brother." The Santorums didn't want Gabriel Michael Santorum to be an abstraction to his siblings.

First, Alan Colmes on Fox News: "Once (voters) get a load of some of the crazy things he's said and done, like taking his 2-hour-old baby who died right after childbirth home and played with it for a couple of hours so his other children would know that the child was real ..."

Colmes was then interrupted by Rich Lowry: "You are mocking him. They lost a child, Alan. That's very serious and it's not something you should be mocking on national TV."

Colmes' response: "I'm not mocking the losing of the child. But what I'm saying is I think it shows a certain unusual attitude toward taking a 2-hour-baby home who died to play with his other children."

In addition to engaging in a cheap and mean shot, Colmes simply made up the notion that the Santorums had brought the baby home for their other children "to play with."

The next day, Eugene Robinson, Pulitzer-Prize winning left-wing columnist for The Washington Post, said on MSNBC, Santorum is "not a little weird. He's really weird. Some of his positions he's taken are just so weird that I think some Republicans are going to be off-put. Not everybody is going to be down, for example, with the story of how he and his wife handled the stillborn child whose body they took home to kind of sleep with and introduce to the rest of the family. It's a very weird story."

Four times Robinson calls Santorum "weird," using the story about the death of the child as evidence. He was wrong on an important detail -- the child was not "stillborn." And, like Colmes, he made up a mocking detail -- that they took the child home "to kind of sleep with."

The meanness of these comments is self-evident, as Alan Colmes realized and later apologized to Santorum. Robinson, on the other hand, never apologized -- as RealClearPolitics, which has no political agenda, correctly reported -- even though repeatedly challenged to do so on MSNBC.

I raise these issues for only one reason: to provide further evidence of my belief that leftism makes more than a few of its adherents meaner people.

I have had many interactions with Alan Colmes, and while we always differ, I never found him to be mean-spirited. I still don't think he is mean-spirited, and though I am not the directly offended party, like Santorum, I accept his apology, because I believe he meant it.

So why did he say what he said?

Because leftism fills many of its adherents with contempt and hatred. It takes a person of great character and self-control to continually imbibe and mouth the mantras of the left -- that everyone on the right is sexist, intolerant, xenophobic, homophobic, islamophobic, racist and bigoted -- and not become a meaner human being. If I believed just about everyone with left-wing views was despicable, I would be meaner, too.

In a previous column, I wrote about Thomas Friedman making one of the classic anti-Semitic libels when he wrote that the reason the Senate and the House gave Israeli Prime Minister Benjamin Netanyahu standing ovations was because "that ovation was bought and paid for by the Israel lobby."

How does a Jew write an anti-Semitic libel? Because he's on the left.

That was the reason Rep. Andre Carson said that members of Congress who support the Tea Party want to see blacks "hanging on a tree." Because he's on the left.

Leftists' meanness toward those with whom they differ has no echo on the normative right. Those on the left need to do some soul-searching. Because as long as they continue to believe that people on the right are not merely wrong but vile, they will get increasingly mean. The problem for the left, however, is that the moment it stops painting the right as vile, it has to argue the issues.