Isn't that because the ones who aren't healthy die? That sounds like saying we shouldn't bother having modern medicine because it causes us to have a lot more sick people. The problem is we wouldn't have a lot more healthy people that way; we'd have a lot more dead people.
That's exactly what the comment I was replying to said.
An alternative explanation is that nature is some peaceful place where no animal ever gets hurt, for any reason... What would be a purely comedic exercise if people weren't believing this one all over the thread.
