Its a great side of the argument to have in a debate.
My first reason is nothing should be killed because there is no reason to kill anything. We do not need meat to live.
My second reason is that we all have a consciousness that is intimately connected with God. By killing unnecessarily we are using our smaller selves to disrupt the greater weave of all things.
Thirdly, lol, sorry this is getting longer than I intended, Life is a wonderful and sacred gift as is our ability to be aware of our roles as co-creators. We should be able to accept our ability to end life with the same grace as we accept our own life.
Thanks sorry for getting carried away. It must begin with us, with each one of us, if we have any prospect of shedding our violent and brutal past and begin to extend the present into a peaceful future.
good luck