Indeed. Another addition to the Predators is temperament, just like most species, they would have an individual personality, so regardless of hunting rules, they can't always be generalized by the actions of one or two. Some Predators might be more sporting and even merciful, others might be just dicks. While others just indifferent.
Technically speaking, we can't really place or compare our morality, rules and sense of honor on to them because just like real life, different cultures of humans have their own society, rules and morality. Like we generally don't don't really care about eating cows and pigs, and we dislike other countries eating dogs and dolphins, but to some other countries, our eating of cows and pigs is considered horrible and atrocious.