I'm not even sure if it's possible. Especially with the store bought models (lesser eCig items) around. A huge difference between smoking and vaping is that when not puffing on a vaporizer, there's no second hand stuff floating around. With vaping, the only chance of someone noticing a problem is if they happened to walk in the stream (not really a cloud) upon exhale. And even if they did that, I'm still curious how much of an issue that truly is. I mean if it is, then you'd think vapers, of all people, would be exposed to that second hand stuff and by now, there would be something noticeable going on with health of vapers.
I've also vaped in front of enough non-smokers, many of whom hate smoking, to realize, vapor pretty much presents a non-issue. I honestly can't remember a time where sitting in a room with non-smokers for say 6 hours (playing cards) and a non-smoking person gave any indication (non verbal or otherwise) that let me know that my exhaled vapor made them uncomfortable.
Vapor simply doesn't linger all that much. If it did, this conversation would be vastly different than the one where we muster up something to talk about as if we are causing some serious (even half serious) discomfort to those around us.
With all that said, I do still think all it will take to change things in this discussion is some independent study where 2nd hand vapor is linked to some serious health concern, like your genitals will shrivel up if you are around 2nd hand vapor long enough. Short of that, and I do think we do a disservice to not be vaping in many places right now, doing our best to educate along the way. Though, I'll note that I tend to be another one of those that is practices courteous public vaping, while often wondering why I'm so courteous, given what is actually involved.