Actually, if you compare areas like prisons and black recruiting for Islam, then you would have to agree with that point. I don't know of any study done in the military particularly, but it is far from a streach to believe this is a trueism, not a "toilet journalism remark".
I will see if I can dig up the article with the poll numbers later on. Will post if I can find it.
LowOiL
I recall reading an article about this by Chuck Colson with regard to his prison ministry. The entire article can be found here:
http://www.leaderu.com/socialsciences/terrorbehindbars.html
Obviously the military is not prison. But with respect to the black muslim question, there may be some of the same remnant hatred of the "white power structure" among some. An excerpt:
"Consider: You’re black, and you believe you’re being oppressed by the white power structure. Along comes a person of color who invites you to join the brotherhood—the most appealing aspect of Islam in prisons—and offers you a means of striking back at your oppressors. If, on top of that, prisoners are taught that the more aggressive they are, the more favor they gain with Allah, you have a dangerous mix."