[@Polybius]

They love war, but killing an entire species, not only is that a waste for a good war, but it also goes against one of the teachings of the religion the Kor'Koran follow. "Your enemies will fight for their home until their last breath, it is an warrior's duty to honor their resolve and face them in combat!"

There's more to that, but that's basically why they are against PKW's. Plus, where's the fun in blowing up all your enemies in one go?