"If you can defend yourself without killing then you should, but if you do have to kill then you can't let their life be wasted. You need to live for them now that they can't. They might not be as smart as you or your companions, but they still think and feel and have lives of their own. Even some of the most vicious Pokémon can be convinced to leave you alone if you work to understand them. Try using the Warp Band on everyone you meet and you'll see how they think. You might even meet someone who will want to stay with you.

"But I can tell you what your own companions think of you if I can talk to them."