Wow, what a broken concept of morality. Especially for people that are seemingly okay with revenge.
"You can't absorb corpses of people because that's somehow different than absorbing corpses of monsters, even humanoid monsters. My morals are obviously correct because I say they are, duh! If you die because you were too weak that's a-okay, as long as you don't absorb already dead people!"
Survival is survival. And the idea that it is even slightly related to necromancy is ridiculous unless you accept that what he is doing is already necromancy, which then already makes him going against your morals. Why don't authors think for 5 seconds before they write this? Another case of "I just want to write something to get likes and views and maybe some money!"