I'm happy to read about development of such opinions in the medical world.
My boss, as a former smoker himself, does not have a very good opinion on vaping - "you're inhaling antifreeze". However, his opinion is very biased by his brother-in-law, who does a bit of everything - smoking, devices that heat tobacco and vaping. Just because one guy you know was not put off from smoking by vaping, it doesn't mean it applies to everyone.
Also, both his parents died of lung cancer around their mid 60s, but in their case, smoking wasn't the only factor (however, it was the main reason). And that's another argument against smoking tobacco, vapes weren't around back then.
I always shut him up with "everyone has the right to do as they please with their bodies, besides, i haven't heard of anyone dying of inhaling the stuff fog machines put out in clubs".
I know that best for our long-term health would be to never inhale anything but air. But the world isn't perfect and none of us are, either. And let's not mention the flux fumes i inhale every day when soldering.
Vaping does it for me and it certainly is the lesser evil.