It’s been less than a week since the Fort Hood massacre, and the country is still struggling to understand why Army Maj. Nadal Malik Hasan allegedly killed 13 of his fellow soldiers and wounded 30 more. We know that Hasan yelled “Allahu Akbar!” (God is great) as he commenced his heinous crime, that he was in frequent e-mail contact with a radical imam, and that he posted lengthy defenses of suicide bombing on the Internet. We also know that the Fort Hood tragedy was the second instance this year of a jihadist Muslim killing American soldiers at a U.S. military installation. In June, Abdulhakim Mujahid Muhammad shot two soldiers outside a Little Rock, Ark., recruiting station.

Army Chief of Staff Gen. George Casey told “Meet the Press” that “speculation” about Hasan’s motives could lead to an even greater crime: “Our diversity, not only in our Army, but in our country, is a strength. And as horrific as this tragedy was, if our diversity becomes a casualty, I think that’s worse.” This is patent nonsense; the strength of a fighting force requires assimilation and following orders. To the extent that diversity in uniform is beneficial, American soldiers gladly testify that they serve with colleagues with Muslim beliefs who perform their duties with distinction.