No, it is stupid, I hate it.
The Preds aren't Mandalorians (for those who have played KOTOR, et al)!
It's not honour, it's hunting ethics. There's no point in killing a sick animal (ie Weyland), as it is no sport. No point in killing a pregnant animal, as that reduces your hunting stock. And a helpless animal (ie being unarmed) is also un-sportsmanlike.
War is totally different to hunting. We haven't seen the Predators in war. The rules of engagement are different in war.