One of the truest observations ever made was by a philosopher who observed that no matter how thoroughly evil a person was, he would always be convinced he was doing the right thing.

It’s a realization that goes a long way toward explaining the mad bombers of the world.

For surely the Tsarnaev brothers, somehow, came to the conclusion that planting bombs at the Boston Marathon that killed three and injured hundreds was the right thing for them to do.

It may be nearly impossible for most of us to see how any path of reasoning could take you to that conviction, but perhaps it becomes a little more understandable when you consider the brothers’ parents.

For every evil person who thinks he is absolutely correct, there’s probably at least one parent who can’t believe their child would do anything wrong.

While there must be some sympathy spared for any parent who loses a child, interviews given by the Tsarnaevs reveal a couple who clearly have some serious delusions — about their kids, their faith — and who, you get the sense, fostered and indulged whatever darkness was building up inside their children.

Zubeidat Tsarnaev and her husband, Anzor Tsarnaev, are insistent that their children were framed and the entire bombing scene staged. “There was paint instead of blood!” said Zubeidat Tsarnaeva on CNN. “It is some kind of show, spectacle … something like a really big play performed by actors.”

Videos showing Tamerlan and Dzhokhar Tsarnaev planting the bombs, plus the many pictures of people with actual limbs blown off would tend to argue against that, but you can understand a mother in pain looking for explanations, even far-fetched ones.

In the parents’ view, Tamerlan was killed by federal authorities while he was in custody, not shot in a gunfight then run over by his own brother. And Dzhokhar, well he was shot in the throat to keep him from talking — literally.

Father Anzor Tsarnaev during the CNN interview expressed a desire to go to the U.S. to “find out the truth.” Asked if she accepted her sons’ guilt, Zubeidat said, “No, I don’t. And I won’t. Never.”

If the parents had shown that kind of determination in keeping their kids away from the influence of radical Islam, the Boston bombings might not have happened.

But you get the impression that delusion was a big part of the Tsarnaev family lifestyle.

The Tsarnaevs, who lived previously in the United States but now live in Dagestan, deny that their boys hung out with extremists. “America took my kids away from me. I’m sure my kind were not involved in anything,” said the mother.

Tamerlan spent a great deal of time at a mosque known by police as a “hotbed” of Islamic radicalism, but the parents deny he associated with exremists.

Maybe it’s a matter of the fish being the last to know he’s swimming in water, but if your family’s religion advocates killing of “infidels” and spreading the faith across the globe by conquering people and killing them when they refuse to convert, don’t you think maybe you should switch religions? Especially if you’re raising children?

We probably all know parents of juvenile delinquents who will defend their children even when they’ve been caught red handed spraying graffiti or throwing rocks. Turning a blind eye to the fact of your children’s growing Islamic radicalism and interest in making bombs is that same syndrome times 100.

Perhaps the parents are Muslim in name only, some of those “religious” types who don’t understand the real tenets of their own faith or the demands mullahs put on young people. If those were the only sort of Muslims around, there would be a lot fewer problems with terrorism.

But turning a blind eye toward the reality of radical Islam, as parents or as a society, can only lead to more acts of terrorism in the future.