Killing is a vestigial instinct in mankind. Our sentience has moved us past it. Most of the time when people kill, it hints towards varying levels or forms of psychosis. If not, it is usually a crime of passion or in some form of self-defence. Usually though, we aren't killers. If you could talk to a spider and asked it if they thought that was okay, they would say yes because she was hungry. That is how they operate. They don't have the same level of sentience as us that allows us to question our morality about such incidents. While we wouldn't consume our mates, that is because 1.) Humans are not cannibalistic in nature. While there some noted examples, it should b known that they are oddities. 2.) We have feelings such as love and friendship. We form stronger and more emotional bonds than other animals do. We actually consider the judgement of our peers, whereas animals try just to survive. They might bow out of the way of the alpha male, but that is typically out of fear as opposed to respect which would be a more logical reason for a human to act the same way towards someone who posesses dominance over them such as their boss, or a parent. While fear of punishment factors into this, I find that it is typically to weak of an emotion in many cases unless the individual is noted for causing significant phyiscal or emotional trauma.