Great questions, let's look at them a little bit deeper. Currently it's impossible for a human to exist without destroying some forms of life. On a small scale, your immune system destroys bacterial life constantly. You personally kill countless insects. Indirectly you support the killing of large mammals for meat and necessary drug testing. It's not the destruction of life that you're protesting, but rather the destruction of human life. What makes humans unique that they should be preserved? Is it a heart beat? No. Brain waves? No. The main thing that separates humans from animals, from insects and bacteria, is consciousness. But then it's still not okay to kill someone as soon as they are sleeping (unconscious). My personal conclusion is that it's not just consciousness in the present, but consciousness in the past, and potential for consciousness in the future. In this sense, it's okay to pull the plug on a brain-dead woman since there is not possibility for future consciousness. Additionally, before a human becomes conscious, killing them is no different than killing a mammal. The difficulty is finding the point where this consciousness begins. My earliest decision-making memories occurred when I was around 6, however I've heard people say it's much earlier. There's obviously some variance here from human to human, and we want to make sure we get a safe lower bound. I'm not suggesting we allow killing all babies under 6 years old. However, I've yet to meet anyone who claims to have been conscious at the moment of conception. To answer this question, explore the question of why killing is wrong (set biblical reasons aside for a minute).