The vapor from a PV is not toxic waste and quite frankly extends no further than your breath. All the vapor does is make the locations where your breath is going more visible.
When I breathe out, I might have a cold and infect someone with a weakened immune system and kill them. I might afflict someone with the garlic from my pesto. If I just drank coffee my breath might even contain a few nanograms of evil caffeine.
I am all for being polite, but I don't think in general it is healthy to take an attitude that what we are doing should be hidden or is somehow any more hazardous to the people around us than breathing.
The problem with smoking is NOT that it is some sort of moral issue akin to child molestation -- though some people (the same ones who would have burned "witches" in prior eras) have done so. The problem with smoking is that it contains carcinogens that could harm your health. Now, 2 out of 3 people who smoke until the day they die never get a smoking related illness. But, hey, who wants to be in the unlucky 1/3rd?
Why should we treat vaping as though it is shameful, hazardous or akin to child molestation? Vaping is NOT smoking. It generates no carcinogens for unwitting bystanders to absorb. And while it can have a faint smell, it is certainly no worse than the smell from the onions on my salad at lunch. It is certainly no more dangerous than me being in public and sneezing -- which could conceivably start the next pandemic flu and kill millions. Do you ask permission of strangers before breathing if you have been eating onions?
I guess what I am saying is that there is a population of stupid people out there whose crusade regarding smoking is a baseless moral witch hunt; and capitulating to them while vaping will only encourage them. By all means, be polite, but don't act as though you are sacrificing virgins to Satan on the sly. You aren't. You aren't doing anything that could harm anyone around you, and since your rights end where harm to others begins, none of them actually has a right to give you a pain.
People might have the power to give you pain, but there is no legitimate reason to do so. The only reason to stop you from vaping is to "punish" you for the "sin" of using nicotine. Its interesting to me how a population of functional atheists still manages to act as though they were managing the Spanish Inquisition.