If US troops had been standing right there on the ground at the time, able to approach and disarm the guy, then it would have been proper to take him prisoner and give him immediate medical aid, if he'd have been willing to surrender. If he had continued to resist then it would have been proper to try again to kill or disable him.

But there were no US troops on the ground there at the time to do any of that. That's why the point is moot. The helicopter crew's mission was to clear a safe path for the follow-on ground forces. Leaving hostile combatants alive so that they could later attack the follow-on forces would have been against their orders, and it would have gone against simple common sense.

Even approaching a supposedly docile (or wounded) enemy combatant on the battlefield is a very, very risky business. Many times they will wait until the opposing soldiers draw near and then detonate a grenade to try to take out a few more of their opponents, along with themselves. In fact, just last week four US soldiers stopped to help a civilian taxi driver who appeared to have been injured in some way on the highway to Baghdad. When they approached him to ask him if he needed help he detonated a bomb he had in his vehicle and killed them all, including himself. In Vietnam the NVA and the VC used to love to place armed grenades under the bodies of their dead (and our own dead as well) so that when you tried to check or move them you got blown to bits.

No, I don't have any problem with it. I feel reasonably sure that if any of those guys on the ground had survived they'd probably still be fighting us today, more likely than not.

War is harsh. Nobody has ever claimed otherwise. It's the breakdown of all the normal rules of civility. Survival and winning take precedence over just about anything else, including compassion. That's just the way it is. Everywhere. That's life. It's just a fundamental part of our basic human nature.