A better solution, given that they did have ground assets in the area at the time (as evidenced by the arrival of a group of IFVs shortly after the engagement) would have been to let the ground forces intercept the van. They have the option of stopping it without killing the people inside.
Remember though, this incident occurred 3 years ago - back then, intercepting the van might not have been possible without seriously endangering the lives of allied troops or civilian. I generally agree with you, but if trying to deal with it peacefully places more lives at risk than those of the presumed insurgents, finishing the job might be a better idea.
And remote drone stuff is basically video games turned real - you are not in the shit so it doesn't affect you *nearly* as much.
On the other hand, UAVs also have their benefits. You know you won't die if your drone gets shot down, so you can take a risk and identify your targets instead of engaging everything that looks hostile just to make sure they won't engage you first.
And there was no excuse for blowing away the minivan trying to carry off the wounded survivor.
Yes, there was. "Better safe than sorry" - once recovered, the guy would likely have been fighting US troops once again. This isn't a regular war where professional soldiers are fighting each other; this is a group of terrorists and insurgents targeting lawful combatants as well as civilians with everything they've got, at every opportunity.
There are also maximum calibers on guns allowed to fire on human targets, above which the gun is classified supposed to be fired at vehicles and equipment.
The controversy over certain types of anti-materiel rounds occurs due to the fact that some of them contain explosive and incendiary components, which are outlawed under the St. Petersburg Declaration (which deals with explosive and incendiary ammunition - and which the US did not sign). It's perfectly legit to fire ammunition of any size at human targets.
At the moment it isn't heading in the nice star trek direction.
You do know that Star Trek is portraying a brainwashed communist society, do you?
"Take that, you hostile sons-of-bitches!" -- James Coburn, in the finale of _The_President's_Analyst_