In war, you make your enemies surrender. You do NOT let them rape and pillage at will and then bid them 'fare thee well' as they make of with what they please. If they don't surrender, you kill them. In that way, they will never consider invading the territory of others again, or fight you ever again. If they surrender, by all means be merciful (though wary), but only then.
As for the comment that 'Kuwaitis never clean things up,' please tell me how Iraq has cleaned up the mess it made? Tell me how gracious it was for the Iraqis to set the oil wells of a neighboring nation alight, and how they pumped the oil into the sea and polluted it, how they tried to foul the water supplies of neighboring nation's desalinization plants, even in defeat despoiling everything they could?
I've got a US flag here from the Gulf War. It still carries the stench of petroleum smoke and is spattered with oil from Iraqi environmental 'concern.' And they left many to speak of their barbarity while 'guests' in Kuwait.
Iraq EARNED the highway of death.
The "Highway of Death" was not laden with refugees. It was full of fleeing Iraqi occupiers trying to escape with as much loot as they could take.
Further, the Iraqi army didn't quit en mass after the cease fire was announced. Case in point: the 24th Mech was attacked while moving out of the combat zone post-cease fire.
The people on the "Highway of Death" got what they deserved.