Oh, no no. We treated prisoners very badly in South Viet Nam, especially when guided by the ARNVNs. Moral was very high. We carried shotguns on point and used beehive rounds in 105mm recoiless rifles.
Soldiers somehow get off on things that they consider to increase their safety and that makes them happy (relatively). They're weird like that.
Marvin the ARVN was pretty worthless at actually fighting, IIRC, and he could not be said to have high morale. And then you copied his treatment of prisoners.
Moral was very high.
You may think it was high. Go back to 'Nam and ask the NLF and NVA folks from your AO what they thought of your unit. You will probably not like the answer.