...I always liked the way it uses the enemy's own beliefs against them. Their religious fervor is one of their greatest strengths.

It doesn't do that at all. As Marc tried to explain, it is based on a mistaken perception of their beliefs and is thus incapable of acheiving the intended effect.

There are undoubtedly many who would say that this is barbaric and not good "strategic corporal-ing".

Its not barbaric - but neither does it have anything to do with good or bad "strategic corporal-ing". Its just juvenile idiocy. It's already clear that it is a positive motivational tool for your average Snuffy "yeah, ####'em, send the bastards to hell!" However, the only effect on the bad guys would be similarly emotional - to piss'em off. Or perhaps they'll just be amused, and snicker to themselves about the stupidity of the infidel as they emplace their next IED ambush. As far as the general indig population - it only furthers their perception of our guys as ignorant westerners attacking a misunderstood aspect of the faith, rather than reaching a real solution to dealing with murderers and criminals.