Rat Poison?

Have been reading the blog of freelancer Michael Yon about his reports from Iraq. It’s a dirtier little war than we thought. Some of the motley crew of ‘insurgents’ he writes about lace the explosives in their bombs with rat poison (Which works as an anticoagulant) in the hope that their victims may bleed to death if not killed by any blast.

I ask these questions; How does any religion or holy book justify that? Or is the belief system surrounding that religion and / or holy book merely being prostituted as an excuse for power hungry murderers?

Anyone got any sensible answers?