As more is learned regarding the tragic shooting rampage at Fort Hood, Texas, there are serious questions concerning how and why Maj. Nidal Malik Hasan was allowed to serve in the U.S. Army.

Well before Hasan killed 13 and wounded 30 others at the army base, he had a history of expressing opinions about military policy in the Middle East, about terrorism and virtues of suicide bombings that should have rendered him unfit to serve as an officer in the United States military.

All who serve in the military have a right to question official policy. But the extent of Hasan's anti-American rants can only be described as disloyal.

News reports say Hasan, a military psychiatrist, had given lectures full of anti-American propaganda that expressed approval of suicide bombings and said the country's military presence in the Middle East was a "war against Islam."

"The system is not doing what it's supposed to do," Dr. Val Finnell, who studied with Hasan from 2007-2008 in the master's program in public health at the military's Uniformed Services University of the Health Sciences, told the Associated Press. "He at least should have been confronted about these beliefs, told to cease and desist, and to shape up or ship out."

Army officials were made aware of these concerns about Hasan, but did not advance them up the chain of command out of fear of being branded as discriminatory toward Muslims, reports have said.

And now, an ABC News report says U.S. intelligence agencies were aware months ago that Hasan had been attempting to communicate with the al-Qaeda terrorist organization. U.S. Sen. Joseph Lieberman has called for an investigation into whether the Army missed signs that Hasan had become an Islamic extremist.

There are many Muslims who serve in the U.S. military with courage and honor. But it seems quite clear that Hasan's stated beliefs made him unfit to serve as an officer.

Military leaders cannot use fear of giving offense as an excuse to avoid asking questions and taking action when an officer's publicly stated views amount to a threat against the country he or she has sworn to defend.