My policy is: if it makes someone uncomfortable and they tell me so, I'll vape somewhere else. No biggie, just not worth the trouble. Doesn't matter if it "doesn't make sense," my job is not to educate non-vapers about what I'm doing. Maybe if you are cool/chill about it, they'll respect you more and actually ask about vaping. Maybe not.
I will say, though, times are changing. In chicago, every time I leave the house I see at least one person taking a vape on the streets. And not just the egos either: mech mods, etc. They're really becoming pretty mainstream.