I usually ask people two simple questions:
If I was a drinker until 6 years ago, and suddenly swiched to non-alchoolic beer EXCLUSIVELY, would I still be considered a boozer, just because I would still be drinking lots of "beer" ?
On those circunstances, would I be dishonest, or "fooling myself" by stating the simple truth that "I used to be a boozer, but I have not drank in the past 6 years" ?
Usually, I get a "No" on both questions. I then point out that people would not ask me "when will I quit NA-beer also". Because the "quitting" had already happened, simply by switching to an alchool-FREE alternative to whatever I was drinking before.
I then ask those people: where is the logic then, in considering someone who has been using a smoke-LESS alternative to tobacco cigarettes, for the last six years, as a SMOKER? No SMOKE, no SMOKEr, by definition...
Some of those people will still tell me that "it is not the same thing". But when pressed to explain why exactly is it not the same thing, they usually can not.
And of course, some of those people will argue about the nicotine. "I would not consider you a smoker if you were using NON-nicotine liquid, just like the NON-alchoolic beer example you gave me".
And here comes the fun: to those, I simply explain that the main issue with SMOKErs is the SMOKE, not the nicotine. That people who have been on NRT's for a year or two are considered EX-smokers. And that not even an anti-smoking doctor would consider his Snus user patient as a smoker. Sure, he will rant about his patient's use of tobacco, and see it as a "problem" to be adressed. But he will NOT consider him a smoker. Not even the most anti-smoking medical doctor would do that.
When those people cannot find anything else to say, I usually end the argument by stating something like "So you see, despite your *beliefs*, the truth is you cannot really explain why am I still smoking, after all. And that's because I really am NOT smoking".
Mostly, I used to get this "you have not quit anything" crap from a family member, a retired nurse. Not anymore.
(On a darker note, she did shut up about me "not having quit", just to start giving me "warnings" about the e-cigarette "dangers" she has been hearing on the news, and how it is "more dangerous than smoking cigarettes". Maybe she believes I DID quit smoking after all, just to embrace a more dangerous "addiction"

)