Personally, I'm against blanket bans.... (I mean, why should we not be able to have blankets?
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Seriously though, I do believe that adults should have the right to choose to do what they want, provided no one else is harmed.
But therein lies the problem! How do you measure the harm done, by anything that we do?
If non-smoker gets lung cancer from passive smoking, there is clearly harm being done to the non-smoker. But if a smoker gets lung cancer, well that's self inflicted isn't it, and no one else is harmed, right? No, wrong! The rest of society has to pick up the bill for the medical treatment required due to self inflicted harm from smoking.
Also, if society in general normalises smoking (as it has), then children are encouraged to smoke by default! Children copy adults.
Preventing children from getting addicted to smoking in the first place is beneficial to them and to society as a whole. That's going to take a long time, however that should not stop us trying.
Weighing general harm prevention against general freedom is not always easy and any rules put in place to do this can be difficult to enforce.
As said, I don't believe in blanket bans. A previous poster mentioned the abject failure of alcohol prohibition in the USA. Not to mention the fact that criminal gangs were essentially given a licence to print money from this law. The current problems of hard drugs in the USA are in part due to Prohibition creating a criminal infrastructure and culture to take advantage of that stupid law.
So, what do we as a society do? Personally, I think that smoking for adults (that is over 21 !) should be allowed, in private and with only other consenting adults present, under licence. The licence fee could include the cost of a private health insurance policy to cover costs of smoking induced illness. (Edit: and an annual mandatory course on the effects smoking has on the body!)
As to increasing the age limit by one year every year; well, it might work for a few years but I don't see it as practical for the long term. A ban on all public smoking and purchase of tobacco by licence holders only would be, IMO, a good thing.