Posted this on another thread but think it's worth to discuss on its own:

Let's take it even further. Everything being mere matter, why should we distinguish between living and unliving? Something that lives simply functions differently from something that doesn't live. So why should, say, humans be allowed to sit on wooden chairs? Or on any chair for that matter? You don't sit on another human being. Or, conversely, since it's alright to cut wood, why is it not alright to cut human beings? Big questions being asked. If you have an answer you are either insane or on the path to sanity depending on what you answer.