I was having a conversation with a friend regarding smoking cessation. After mentioning that I began using an e-cigarette, he referred to it as a "healthier" alternative. I refuted by stating that it is a "less unhealthy" alternative. He agreed that I am correct, however stated that his use of "healthier" was also correct. His argument was that the baseline of health was not a constant in the situation, instead was fluid and moved to the mark of the level of health that smoking a cigarette is in comparison. My view is that "healthier" implies that it is on the side of the spectrum of positives, not being less negative. Am I incorrect in this view?
I mostly agree with you ( that "healthier" implies augmentation to some baseline ) and would say that your friend is "playing with semantics" ( although I'm almost reluctant to use that phrase because it's so heavily abused that jaded readers may dismiss the rest of what I say when they encounter my usage of it ).
There is in fact a baseline of health that is "absolute", which is a person's health without any unneeded additions or deficits; that is to say, someone who has adequate sustenance, shelter, exercise, and sleep is about as healthy as they can get. From that baseline, any form of smoking or vaporizing can only be neutral ( at best ) or harmful, so using a positive ( "healthy" ) to describe it sounds a bit strange. It isn't unusual for people to reframe potentially harmful behaviors in ways that allow them to rationalize the continuation of those behaviors. But your question isn't about psychology, so let me return to the subject at hand. :-D
Colloquially, most people would accept your friend's claim because the baseline isn't explicitly stated; your perspective is "assuming someone is not already smoking", and your friend sees it as "assuming someone is already smoking", so you are both "right", but are not actually talking about the same thing, because the contexts of your claims differ.
English allows a good deal of "awkwardness" in linguistic construction, so "less unhealthy" can be understood, but in general -- and this probably applies to most languages -- a smoother sound is obtained by avoiding negative prefixes ( in this case, "un" ) and using a word that contains the meaning that the negative prefix would yield anyway -- in this case, instead of "less unhealthy", I would say "less harmful".
Of course, there is a caveat: if you say "less unhealthy", at least it is clear that it is "health" that it affected, whereas "less harmful" doesn't necessarily make clear that is being harmed. Colloquially, again, though, when most people hear or think "harm", they tend to think first of themselves or others, so if you said "e-cigs are less harmful", no one is likely to think that you are talking about, for instance, reducing the resale value of ( "harming" ) your car.
It comes down to whether you just want to compare the two, or whether you want to burden the sentence by implying there is some standard reference value of health (such as the health of non-smokers).
Saying "e-cigarettes are healthier than regular ones" is a proper way to phrase the argument if it is a straight-forward comparison. If there is a standard of health, then there are three permutaions of the standard, e-cigs, and regular cigarettes that each have e-cigarettes healthier than regular cigarettes. Saying e-cigarettes are less unhealthy than regular cigarettes is more precise in that it refers to only one of those permutations.