After we got rid of that pesky Taliban and rebuilt their nation? The old phrase was, win their hearts and minds? Besides, we already took over Afghanistan, remember? Did we get Japan and Germany on our side during their occupations by doing crap like this? Dehumanization should stop sometime after victory.
Yes, this goes on in every war. Yes, it's a common, psychological effect. So, shouldn't you be surprised, ten years after we "won" that this is still going on, and that you still think our situation is so precarious that this is expedient? It's a sign we've lost. If we're dehumanizing Afghans now, we're never going to accomplish our goals there.
All Afghans feel the insult, including those in Karzi's government. Islam has laws on how to treat the dead. To desecrate these bodies is anti-Muslim. Even if those guys were terrorists and didn't deserve a good burial, their families still need consolation. Funerals are for the living. You won't shed any tears, but apparently you've forgotten that desecration of the dead is considered insulting to any culture.
We didn't see law enforcement posing with John Wayne Gacy's body parts, and it would horribly unsettle people about police in general if they did, and that's within our borders. You simply don't do that when you're trying to bring people to order.
No one asked you to shed any tears in grief, only in defeat.