While hunting, I choose a weapon that I KNOW is capable of quick clean kills, as long as I do my part. Hunting has been around long enough to show in history that certain weapon/ammo. combos are very good while others lack in ability to make quick kills consistantly. Of course, there are an unlimited amount of hunting situations, so I have to choose the weapon for the situation that I most likely will find myself in while hunting any certain species, and then do my part in making a quick clean kill. It don't always happen, BUT I know I can't blame the weapon/bullet choice.
As far as hitting animals with a vehicle, that is often out of a persons control and I personnally don't always have a gun with me, BUT seldom does a 2# critter get run over by a 7000# vehicle and have any life left in it. I have hit two deer over the years, and one of them ended up in the freezer because he didn't take a direct hit and had to be shot to be finished, and the other was a doe and she went completely under the vehicle and was hamburger at the sight, stopped and drug her off the road so she wouldn't wreck someone elses vehicle. Althought that's all beside the point, because trying to compare how we as hunters treat animals while hunting to aniamls that are hit by vehicles is quite a stretch and not really comparable because in one situation we have control on how, when, why, where an animal dies, and with a vehicle we don't!
I've often questioned why is it wrong to shoot a pheasant, dove, or the likes while not in flight, yet it's fine to shoot a rabbit while sitting, a turkey while standing, etc.?