I've thought since I started vaping, what if I was the one being forced to smell the person vaping. Inside rooms, hallways, indoor public places, stuff like that even though vaping may not be expressly prohibited in places like this it's rude to force somebody to smell what you're vaping it's like the person that wears too much perfume and it makes you gag. What if it smells like that to somebody?
Now that being said, walking outside in public spaces where unless I exhale directly into their face it would be extremely unlikely they would either smell it or run into it, I vape away. As long as I watch who's around me and make sure I don't blow a cloud into someone's face, there's no problem. Even if somebody passing by is allergic to something in the vapor im exhaling, flavoring, pg, something like that it will dissipate before it reaches them so there's no harm.
So, as long as I can make sure I'm not forcing people to sit in a cloud, I vape away. Walking down the street, sitting on a bench, unless you run directly for the vapor I just let out there is no way it can bother you besides the obvious visual. People see things that bother them everyday, now when it's something like this where relatively speaking it is harmless I always give the person two options. They can either get over themselves or they can ask a question and I spend the next few minutes correcting all of the misinformation or ignorance the person has been living with.
After all of that, if my vaping is bothering anybody (assuming they are being reasonable, maybe the wind is carrying the smell or something) I either try and exhale differently or move a little bit so they aren't being affected. If I can't do that then well, I can go without vaping for awhile, no big deal.