You know very well though what is meant with "humane killing"

Just form comparison; do you think that animals in the wild all live in heaven without any pains ?

People are omnivorous, like many animals out there, is it okay that animals kill? If yes, then why is it wrong that humans kill? If no, I don't know what to tell ya

We also pretty much NEED leather. Until factories can produce real leather, how do you propose to do that without killing animals?

We can remove everything bad but by then there will be very little left to live with

I'm not saying it's nice to slaughter animals, but since it's pretty mcuh a necessity, at least we can try to make sure they have a nice life that suddenly stopped. It will still be a 100% nicer life and death that pure nature can give them.