I remain puzzled why you keep asserting this point (which is central to your argument) as if it were a truism, when it is far from self-evident.
To my mind, your argument is tautological:
1. Killing is inherently wrong.
2. Therefore, no act of killing can be justified, even if it might result in outcomes that are desirable (eg saving innocent lives).
The problem is that point 1 is an a priori axiom, rather than something that is established by reasoning.
Contrary to your assertion that killing is killing, there are many shades of grey, which the laws recognise and try to deal with. Your own acceptance that it may be justified for self-defence acknowledges that. Even self-defence has shades of grey - eg what is a proportionate response to a threat?