As we learn more about Maj. Nidal Malik Hasan, the accused Fort Hood killer, what we discover is deeply disturbing _ but not as disturbing as evidence piling up that military authorities knew for months, if not years, that he had displayed radical Islamic tendencies and did nothing about it.

The portrait now emerging is that of a troubled loner who turned increasingly to his Islamic faith for consolation.

The form of Islam to which he turned, though, appears to have been a radical, highly politicized version that he may have first encountered a few years back at a Virginia mosque (the former imam of which, now living in Yemen, praises Hasan as a “hero”).

Many who knew Hasan, including fellow Muslims, relate that he often spoke about his religion-based opposition to the U.S. war effort. In one PowerPoint presentation, he framed his objections in terms favored by Islamic terror groups _ that is, that the war on terror is a war on Islam.

This could not have been a secret to the U.S. military, based on his apparent openness with fellow soldiers. Some who worked alongside Hasan have said he shared his religious radicalism freely.

Colleagues at the Walter Reed Army Medical Center, where Hasan, a psychiatrist, was posted until his transfer this summer to Texas’ Fort Hood, reportedly say that he delivered a bizarre religious lecture proclaiming “infidels” would be tortured for their lack of faith. Other doctors say they felt afraid to complain for fear of looking as if they were picking on a Muslim colleague.

Dr. Val Finnell, an Army physician who did speak up, now says, “The system is not doing what it’s supposed to.” Plainly not. Worse, ABC News, citing unnamed intelligence sources, says the CIA knew months ago that Hasan was trying to contact al-Qaeda. If true, it’s scandalous that a would-be freelance jihadist was allowed to remain on active military duty.

Sen. Joseph Lieberman, chairman of the Homeland Security Committee, has rightly called for a congressional inquiry.

The American people _ and the families of the dozens of U.S. soldiers killed or wounded in Hasan’s bloody rampage _ deserve answers.

At a minimum, they are entitled to know whether the government could have stopped Hasan _ and why it didn’t.

It’s understandable, commendable even, that Gen. George Casey, the Army’s chief of staff, worries about reprisals against Muslim troops. They should not be unfairly tarred with Hasan’s foul deed.

Yet the best way to prevent that is not through politically correct diversity lectures but rather by making sure no Muslim serving in the armed forces is an Islamist rooting for America’s enemies.

After 9/11 and eight years of war, one might have thought this to be basic common sense. But again we see the wisdom of George Orwell: “To see what is in front of one’s nose needs a constant struggle.

• McClatchy-Tribune News Service