As a human being with my own rule over my own body I have the right to do with it as I please.
If I want to consume addictive cancer sticks until I die a slow, painful death, I have the natural freedom to do so, and laws, taxes or fines won’t stop me until I’m really locked away.
So I support other peoples freedom to smoke. It is just inhaling smoke from burning plant matter, which may be an irrational choice, but is my choice.
While I see your point, this could be extended to people doing dangerous sports for fun, eating unhealthy foods or engaging in any activity where one could get hurt.