If you rephrase to "inhaling anything but fresh air is worse than inhaling fresh air" I think it's not just a myth. Our lungs are self-cleaning organs (gotta love those). However, the real question is "Is inhaling what we vaporize bad?". As to which no one can answer with certainty. Can't help but wonder if I cough and get a taste of Butterfly Bait or somesuch in my mouth. I still choose to see it as less harmful than smoking until proven otherwise, and will keep blowing little fluffy clouds. Jokingly, in case of a zombie apocalypse, I' thinking the zombies will find my lungs awesome tasting... and they'll have to chase me slightly further to get at them thanks to not smoking.
There's no denying we're setting a precedent for stuff usually not inhaled in great concentrations. Only time will tell.