An objective of any good parent is to try and shelter or save your offspring from making the same mistakes you made. Your fathers apparent long time struggle with tobacco products have obviously left some sort of residual psychological scar which isn’t uncommon in ex-smokers. From what you say, he very much wants to protect you from going down the same path he went. Even though you are legally an adult, in your parent’s eyes your coming into maturity may be a long time off, especially if you’re an only child or the youngest. Keep in mind that even though you are taking the path of a lesser evil, it can still be habit forming, not to mention financially draining, all of which are concerns to parents of younger children, especially parents who are unwilling, for whatever reason to completely let go. However, even though your parent’s intentions are noble at heart you must stand on your own feet, it’s important for you to set your own boundaries and for your parents in turn to respect those boundaries. Understand that if you live in their household you will have to obey, and live with whatever rules they set; it is after all their house. If that means no tobacco products of any kind allowed in the house you’d have to find someplace else to store your newfound hobby. Until you come completely independent, rules are still rules. Even when you are independent there will still be rules, they just change.
Just my .00002 Cents
Chris