People don't choose life - it is forced upon them. If they want to check out, they should be able to do so at any time. In my opinion, most people are against suicide typically because they are selfish. They want to keep their loved ones around as long as possible, without any regard to how it actually effects that individual. Of course, most people aren't going to think abstractly about the issue anyway, so I don't think it would do much good in trying to convince them. They've been indoctrinated to think that life is precious and perfect, and until that illusion breaks there isn't much hope in arguing the point.