Wow. Appalling. Also another incarnation of the equivocation on what it means to believe.
Well, it kinda makes sense. A person who is already brainwashed by religion is easier to brainwash for the army as well. An atheist already questioned one authority, so why would they be good puppets, ahem, I mean soldiers?
I hadn't thought of that angle. I suppose a certain willingness to defer uncritically to authority characteristic of religious association might predispose a person to do so in a military context, so the armed services might naturally prefer religious people, finding them generally more malleable. More likely, such people may themselves find military authority appealing because comfortingly familiar. But for others who choose military service, for whatever reason, there's that pesky first amendment...
People are, of course, free to sacrifice themselves to a greater evil.