Such policies save American lives because the enemy is more likely to surrender sooner when the tactical situation is not in his favor.
Americans have a reputation of treating prisoners well and this reputation helps our soldiers. We do not want the enemy to fight to the last round or try to break out from a surrounded position which they likely will do if they think that they will be tortured and killed if captured.
I agree. Hitler actually issued a special Fueherbefehl (Order from the Fuehrer) just prior the to the Ardennes Offensive ordering the German Army to show the enemy no mercy. He clearly intended for the level of savagery on the West to match that on the East.
It had become apparent to the German soldier that he was probably better off surrendering to the Western Allies than fighting to bitter end. The German soldier by this time had no particular fondness for the political leadership and many on the Western front were too well aware of the lopsided Allied material advantage to hold out much hope of victory. They fought on more out of dogged loyalty to their homeland.
For the most part, much needless bloodletting was avoided on the Western Front and Germans did not generally fear surrendering to Americans or British troops and treated prisoners as decently as conditions permitted, despite Hitler's efforts. (Many of their comrades were Allied prisoners and it was a prospect they all faced.) Even for the SS, Malmedy seemed more an aberration than the norm.
This is true when you are fighting regular troops, but it is just a tactic to be exploited by fanatics. The Japanese were not impressed and frequently did fight to the last round. Similarly, terrorists are not prone to such western concepts of self preservation because the entire point of their actions is to win or die as a martyr.
And I am sick of hearing about our enhanced interrogation techniques creating more terrorists. I am not aware of a single American POW since WWII who was not tortured or at least had the crap beat out of him after capture. Why? Because they know they can do it with impunity and there will be no similar response to their side.
Each conflict should be evaluated individually and our policies based on one thing and that is how they treat our troops. If you give our guys a break we will do the same. If you ignore international norms we will not bind ourselves to them unilaterally.