Why should a government tell us what we can or can't do to our own bodies in our own homes?
It shouldn't. But if your actions put a strain on the Health Service then it has a right to try to get you to stop, or to make what you're doing illegal if it think's it's serious enough.
Smokers have it easy right now in terms of smoking in their home and smoking in their car etc. Personally if there were kids in the car (especially) or the home, I'd charge the parents with Child Abuse.
Let's not get into another Right to Smoke debate, we did all that when the smoking ban was the issue of the day. Suffice to say that smoking iterferes with other people far more than smokers generally accept.
The same would apply when considering legalising other drugs. You are not simply screwing with your own body or mind, you'r actions so have consequences for the people around you and for wider society, and the state has a right to try to control those consequences.
And yes, this logic in principle would extend to trying to control the kind of food people eat, or the amount of excercise they get. E.g. the New York moves on Trans Fats.
I know how you feel though. My vice is driving, I enjoy it. I really don't like the way it's taxed in Ireland, even though I accept that the government have a right to tax behaviour they see as undesirable.
-Rd