I don't recall that, during World War II, any Christians in the U.S. Army agonized about being forced to fight other Christians in the armies of Mussolini or Hitler, or of occupying Christian land where they were not welcome. I don't remember any Japanese in the 442nd worrying that they were fighting the Axis, of which Japan was a part. We were all mere Americans fighting enemies of America.
In fact, I don't recall any Shiite Muslims having any compunctions about killing Sunni Muslims (and vice versa) during the Iran-Iraq War (the "impossible" war among Muslims). So why would anyone in the press try to excuse the mass-murderer/traitor's actions by pointing to his fear that he would be forced to fight fellow Muslims? First, as a Major and a psychiatrist, he would never be fighting anyone, and second, he was a native-born American assisting American warriors in their battle against sworn and declared enemies of America. That should be enough for anyone in the Army. What he did was treason — pure, simple, and inexcusable. Motivation is irrelevant.