Life demands death. Life demands nourishment from other living organisms. It is not a matter of justification it just is a fact of life. It is sad but still it must be done. If an animal continued to decimate your garden (which is filled with living organisms) to the point of killing your chance to survive. You could die or kill the animal. Would you eat the animal or use it as compost? Death can be viewed as a cruel master no one can claim to avoid, or another part of the life process, the next step so to speak..