But the pogemon government and the human one are already in the process of finding ways to stop this from happening again. If he can be permanently enclosed in a pog, they might even consent to us taking the pog with us, effectively removing him from this world entirely.

It's not that I don't agree that he is deadly and dangerous, and if he succeeds would spur others of the same mindset to pour out of the woodwork. But we're going to stop him. And unnecessary killing is cruel and sets us up to be tyrants to any and all worlds we come across. It's not our job to do the planetary governing for them. It's our job to make sure that this incursion is stopped and the planet is safe to make their own decisions.