Oberon: “...you reward yourself with whatever you like to do with your body as long as you are willing to accept the risks.”
As a matter of individual choice, you’re right. I think people should generally have the right to do whatever they want to themselves. However, we live in communities. We aren’t just individuals making individual choices purely for ourselves.
Oberon: “If you start from the assumption that your body is a collection of highly fortunate chemical reactions, then why shouldn’t you do whatever feels good?”
Just because something feels good doesn’t mean it’s healthy or natural. Antifreeze, I’m told, is nice and sweet. I bet it would taste really good over ice on a hot day. I even remember when wine makers illegally added it to their products to improve taste. Doing what feels good in this case would likely result in death, but hey...
Well, granted. But in a world in which people assume there's no God, why should anyone care about your particular notions of what's healthy or natural?
It works out to a very good justification of your own choices in the matter, but people will not respect your efforts to apply what they see as your personal standards to their lives... and nor should they, on those terms. It's just a different flavor of the Nanny State.