I feel like the concern there would directly be secondhand nicotine in the vapor, which is particularly neurotoxic to developing brains [1]. Feels like a pretty reasonable concern to me, with a child around?
> The emissions discharge water, volatile organic compounds (VOCs) and nicotine into indoor air at levels far lower than found with tobacco cigarettes (Schripp et al., 2013).
http://www.treatobacco.net/en/page_528.php
In addition, e-cigarettes dont always have nicotine and often have lower amounts than cigarettes. Further making the fear of momentarily sitting near someone smoking an e-cigarette outside almost irrational in terms of health risks.
In terms of not wanting vapor being blown in your face, then I agree there is a social etiquette that should be respected.
And yes, if once talked to, someone continues to bathe themselves in scents that gag other people, they need to be let go. The flagrant disrespect for people who have to be around you for 8 hours a day is too much.