I believe you have made an error in logic. There is no moral justification for any act. That consideration does not apply. There are ethical standards though, and even animals have them. Another error in logic is to assume harm is necessarily cruelty. Around January 10 I was given a drug I do not know the name of, and when I asked the pretty girl injecting it into me what it was for she said 'To make you forget everything that's about to happen.'
Alarmed, I protested. However the drugs she'd given me kicked in, and I passed out as she began shaving my groin. While I was passed out they cut holes in my veins, and stuck things in them.
Do you doubt any of this was harm?
After the cardiologist placed the stents in my heart, I was moved to the ICU, and to the Cardiac Unit the next day, and the day after that I went home.
Sometimes to do a great good you must do a little harm. That pretty blond helped save my life, but she sure alarmed me with her honesty about the drug she was giving me.
I was raised on an island in Alaska, probably feral in your eyes. I foraged, fished, and hunted for my food from my earliest youth. I was never once cruel. I can certify I was far more humane than any other predators those fish or deer could have died by. It was not my ability to reason, my intellectual capacity, that granted me the right to take their lives and eat their corpses. Neither is it that which grants wolves or sharks the same right.
It is the need to live. It is a fact of nature than predators kill to live, and humanity are predators. It is our natural place in the ecosystem to take prey. The deer understand this, and flee rather than arguing ethics.
All life is born, suffers a while, and then dies, their suffering over. None escape this, not even the plants and fungi vegans claim are ethical to kill and eat. I reckon that just because something is less like us that does not give us some advanced right to kill it, and not things we think are cute and cuddly.
More importantly, there is one living thing on Earth, and all of us from microbes in the mud at the bottom of the ocean to eagles in the sky are part of it. When the first living thing became alive, however that may have happened, it thereafter reproduced. It likely split in two, and those two split in two, and so on, for a long time. For that whole time, each new life sprang from the living tissue of it's progenitor, and until today, that process of living cells becoming new individuals continues, never having died.
We are part of an immortal life form that includes every living thing on Earth. We are more than brothers. We are one flesh. There is no more or less right to kill our flesh of one form or another. We are human, so we should be humane, and insofar as we fail to be, we should be corrected.
But killing is necessary to all life, and as we live we must kill to eat.