Because only Germans ever killed POWs in WW2
We have to remind the ignorant movie going public of this fact again and again, in case they try to think for themselves.
Also... we have to claim a commando unit puts "honour" above all else when by definition said commando unit's mission is to sneak around in the dark bombing and sabotaging things behind enemy lines, stabbing sentries in the back in the most dishonourable way possible, and generally fighting war in exactly the same way as today's "terrorists" in Afghanistan.