I remember seeing an article talking about how this sort of stuff (peeing on corpses of the enemy) happened all the time in warfare. It's one of the ways soldiers cope with the fact that they are murdering other people who are sons, brothers, maybe fathers etc. by dehumanising them. Look at how people often stole the wallets and valuables of dead enemies, even down to their gold teeth! This happens all the time in war, it's just never reported on.
There's a reason the phrase "War is Hell" exists. It's not just like a COD level, or an extended trip to the firing ranges. War will mess you up. It can and has sent men insane due to the emotional, psychological and physical trauma people experience, and many have to go to some extreme lengths to keep their sanity, if that means dehumanising the enemy to the lengths that you feel nothing when defecating on their corpses, or searching their lifeless skulls for gold fillings, then I am in no place to judge them. Every force in history has been guilty of pretty much the same behaviour, and many did a lot, lot, worse.