Claiming the harmlessness of second-hand vapor (when no long-term studies of the harmlessness of first-hand vapor have even yet to be done) is simply not a credible position to take in the context of imposing that second-hand vapor on others. When people have been conditioned to associate second-hand smoke with real potential harm, it is going to take more than mere reason and supposition to persuade them to believe otherwise about a visible second-hand vapor coming from a person who appears to be smoking.
There is nothing wrong, unfair, nor inappropriate about this. It is just the way it is. For now anyway. And with effortless stealth vaping being so much of a welcome improvement over the old smoke or no smoke world, I think we can afford to be patient and understanding until the facts have been verified.
Claiming non-existing rights just makes us villains ... again.