Re: Health issues ( compared to smoking)
To be honest most people refuse to consider any opinion on any issue that is contrary to what society says so unless your parents are unusually broad minded or honest my guess is that you'll be wasting your time.
Basically, the truth is that the risk of cigarette smoking has been so radically over stated by politically motivated junk science that a major effort is needed just to wade through the literature to see what is actually being said. What is really deplorable is that almost everyone has never read, or seemingly has the the ablity to read, with a critical eye what the actual studies say. Instead, they read extremely biased reporters that know nothing about science and instead are pushing a regulatory agenda to suit a political agenda.
I have put up huge amount of material on the subject here so dig around in the archives for the citations. Good luck with presenting your case.