Psychologically, the Ft. Hood shooter's actions—though reprehensible—are, I think, understandable: race and religion are so deeply rooted within our psyches that the moral call for us to rise above our racial and religious differences, by aligning ourselves (psychically) to our nation's racially and religiously agnostic ideals—especially when we are involved in active military service of our nation (the U. S.) within a foreign country that our nation is currently waging war against, the citizens of which are of the same race and religion with which we ourselves identify—is, quite naturally, resisted by our psyches, a resistance that can issue an even higher moral call to us: that we stand alongside those with whom we identify racially and religiously before we will stand alongside those with whom we identify politically and ideologically.
I'm not at all saying that the Fort Hood shooter was justified in what he did; I'm only saying that his psyche must have been torn by the issues I've mentioned here. No doubt he was torn by many other psychological issues as well, but the deeply rooted nature of race and religion definitely played the major role in his violent actions.
I've experienced these deeply rooted racial and religious feelings and emotions and I can tell you that they will trump all other influences, no matter how sensible these other influences may seem to be.
A simple example of this occurred when the U. S. and NATO waged war against Serbia (during the Bosnia-Herzegovina crisis) of the nineties (which was NATO's first offensive). All the guys I was working with at the time were saying that if they were sent to Kosovo they would be kicking some Serbian butt. I was the only one who said that I wouldn't be kicking any Serbian butt because I would be on the side of the Serbians, whom the Russians also supported, kicking some U. S. and NATO butt.
Why? Because the conflict in Bosnia-Herzegovina was deeply rooted in both race and religion; dating back, as it did, to fourteenth century conflict between the Muslims and the Orthodox. The conflict shaped up as being the white, Orthodox Serbians and Russians against the brown, Muslim Bosnians and Albanians, whom NATO, the U. S. and the entire Arab world supported.
It was simple to me: A bunch of white people who were Christians were fighting a bunch of brown people who were Muslims, therefore I simply belonged with my own kind in the fight. There's a deeply felt family-like bond with which we identify when it comes to race and religion, which is not easily overcome, nor do I think it always should be overcome (as in the case with the Bosnian conflict mentioned above). It seems a part of our human nature. I have no animosity toward anyone of any race of religion, but when the shooting starts I will default to my most basic instincts, as I think many (most) of us will. Basic instincts will override higher intellectual ideals almost every time and that should come as no surprise to us.
The Ft. Hood shooter seems to have gone through an experience similar to my own: having to decide whether to fight alongside a people of a different race and religion against the people of one's own race and religion. The major difference being that I didn't actually face this dilemma and he did. I sympathize with the torment his psyche must have suffered due to this but I certainly don't excuse his reprehensible actions.