I agree to a point.
That's all I shot with for most of my life; however, if I were going after people and planning on taking shots of two hundred yards or so, I'd always opt for a good scope.
Case in point:
You've not seen a sniper in the military using open sights since they quit using the Springfield '06.
We don't know how far these shots are. We're hearing everything. For me, with open sights, 200 yards is a long way off but basically, if I can see it, I can shoot it. If I needed to shoot a man at 200 yards with open, iron sights, I'd hit him, but I'd be pushing my luck to be going for one shot head shots.