So is this theory of veganism to not cause pain to an animal? If so what about ethically sourced meat. Like bullet to the head/decapitation. Most of those creatures feel nothing, they just end.

Or is it to not eat anything that comes from the an organism from the Animalia kingdom because harming animals is immoral?

After proofreading, these sound more aggressive/argumentative than i had intended but they get the point across.