FBI, the Pentagon and even his medical colleagues were aware of Fort Hood shooting suspect Nidal Malik Hasan's extremist ideology have raised serious questions about the U.S. military's ability to screen, monitor and remove dangerous personnel from its ranks. But far from justifying the discrimination against patriotic American Muslims predictably called for by the usual suspects, the Fort Hood bloodbath should remind Americans that extremisms of all stripes have no place in the armed forces of the United States.

A nation which has chosen to depend on an all-volunteer military must have clear standards for admitting and retaining those courageous few who wish to serve in its name. Needless to say, they should not pose a threat to themselves or their fellow servicemen and women. They should uphold their oath to the Constitution of the United States and its government. And importantly, they should not undermine either American national security objectives or our timeless democratic values by advancing their own.

To be sure, as the always execrable Michelle Malkin fumed in the wake of the Fort Hood slaughter, potential Al Qaeda sympathizers and possibly deranged Muslim extremists like Major Hasan and Sgt. Hasan Akbar must be prevented from entering or quickly weeded out of the American military.

But the danger to America's security at home and goals abroad hardly ends there.

Consider the growing infiltration of neo-Nazi groups within the armed services. In 2006 and again in 2009, the Southern Poverty Law Center, a group which monitors racist and right-wing militia groups, concluded:

A decade after the Pentagon declared a zero-tolerance policy for racist hate groups, recruiting shortfalls caused by the war in Iraq have allowed "large numbers of neo-Nazis and skinhead extremists" to infiltrate the military, according to a watchdog organization...

The report quotes Scott Barfield, a Defense Department investigator, saying, "Recruiters are knowingly allowing neo-Nazis and white supremacists to join the armed forces, and commanders don't remove them from the military even after we positively identify them as extremists or gang members."

That zero-tolerance policy was put in place in the aftermath of the devastating Oklahoma City bombing which killed 168 Americans, the largest death toll from a terrorist attack on the U.S. homeland before 9/11.

As the New York Times recounted:

The 1996 crackdown on extremists came after revelations that Mr. McVeigh had espoused far-right ideas when he was in the Army and recruited two fellow soldiers to aid his bomb plot. Those revelations were followed by a furor that developed when three white paratroopers were convicted of the random slaying of a black couple in order to win tattoos and 19 others were discharged for participating in neo-Nazi activities.

But a more widespread if more subtle threat to the success of America's military and foreign policy objectives may be the creeping Christian fundamentalism extending throughout the U.S. Army, Navy, Air Force and Marines.

The aggressive push to entrench Christian conservative personnel and propaganda at all ranks of the armed services manifests itself with growing frequency. An early warning came in 2003 in the guise of Lt. General William Boykin. Boykin, who later became a deputy under secretary of defense, claimed during speeches to prayer groups and churches that militant Islamists sought to destroy America "because we're a Christian nation." General Boykin also explained to evangelical audiences that Muslims worship an "idol" and not "a real God." While President Bush expressed his disagreement (noting Boykin "didn't reflect my opinion" and "it just doesn't reflect what the government thinks"), Boykin remained on the job.

Meanwhile, evangelical proselytizing at the Air Force Academy makes a mockery of both Pentagon policy and American values of democracy and religious freedom. In May, 2005, Lutheran minister and Captain MeLinda Morton was removed from her post after warning evangelical Christians were trying to "subvert the system" in trying to win converts among cadets at the Academy. A June 2005 study at USAFA described other incidents of religious intolerance, insensitivity and inappropriate proselytizing, and concluded:

"Additionally, some faculty members and coaches consider it their duty to profess their faith and discuss this issue in their classrooms in furtherance of developing cadets' spirituality."

Even minor restrictions on proselytizing produced an avalanche of opposition from Focus on the Family, the Christian Coalition and other groups which protested that new proposed guidelines abridged "the constitutional right of military chaplains to pray according to their faith."

Undaunted, the push to proselytize in the U.S. military continues. In 2007, an inspector general's report highlighted ethics violations among current and former officers, including two major generals, for appearing in uniform for a promotional and fundraising video for the evangelical group Christian Embassy. As the Washington Post noted, the report "offers a vivid picture of how inappropriately intertwined Christian Embassy had become with Pentagon operations by the time the video, with its extensive scenes inside the Pentagon, was filmed in 2004." Nonetheless, the New York Times reported earlier this year that military personnel were shown videos featuring football's Terry Bradshaw professing his Christian religion as part of an official military production dealing with depression, suicide and "the importance of faith."

The blind eye turned towards these extremist ideologies may not merely overlook the next Terry McVeigh. At a time when the United States is trying to win hearts and minds among Muslim faithful in Iraq and Afghanistan, the new crusader culture risks undermining the fight against Al Qaeda.

As Jeremy Scahill documented in the Huffington Post in May, these kinds of incidents are an affront both to the U.S. military code of conduct and America's Afghan allies:

Lieutenant-Colonel Gary Hensley, the chief of the US military chaplains in Afghanistan, is seen telling soldiers that as followers of Jesus Christ, they all have a responsibility "to be witnesses for him."

"The special forces guys - they hunt men basically. We do the same things as Christians, we hunt people for Jesus. We do, we hunt them down," he says.

"Get the hound of heaven after them, so we get them into the kingdom. That's what we do, that's our business."

(The U.S. military later confirmed that Bibles meant to be distributed to Afghan civilians were destroyed.)

After that embarrassment, Joint Chiefs Chairman Michael Mullen reminded his countrymen:

"It certainly is, from the United States military's perspective, not our position to ever push any specific kind of religion, period."

In the wake of the Fort Hood massacre, General George Casey, chief of staff of the Army, explained one reason why:

"As great a tragedy as this was, it would be a shame if our diversity became a casualty as well."

Which is exactly right. Americans are still trying to determine whether Major Nidal Malik Hasan was a would-be Islamic jihadist, a disgruntled serviceman, criminally insane or possibly all of the above.

In the mean time, thousands of Muslim American soldiers, sailors, marines and air force personnel continue to defend their countrymen around the world. Some now reside at Arlington National Cemetery, like 20 year old Army Specialist Kareem Rashad Sultan Khan, having given their lives for our nation.

Which is why it is so essential both that Americans now resist the dark urge to prevent Muslims from serving in the United States military while remaining vigilant in keeping religious, racial and political extremism of all kinds out of it.

NOTE: For information on how you can help support the victims of the Fort Hood tragedy, visit the BBB listings for the Fort Hood Chaplain's Fund, the local Red Cross, USO Fort Hood, Fort Hood Fisher House and other charities serving Fort Hood and the Killeen, Texas community.

(This piece also appears at Perrspectives.)