They are hunting for sport. Every sport have their own rules. Preds follow the rules, but it is up to them which prey will they choose. A man with minigun is thesame threat as Alien, tyranosauric type of creature from troophy room and every other species they are hunting. If the creature was to easy to kill nobody would try to do so because it would be out of adrenaline. And that is what they are looking for. They do not eat preys, they are collecting skulls, skins and ocasionaly weapons or other sagnifican parts of their preys belongings. And I do nto agree that P1 Pred was young and unskilled, he was smart enough to stay away from the guys with minigun and machine guns.