Ok, firstly it
isn't water vapour - it's mostly PG/VG mist, some water, some food flavourings and
maybe small amounts of nicotine (plus whatever else you've got in your lungs that decides to hitch a ride

)
Is it harmful? To you, unlikely (and much, much safer than smoking) - to bystanders,
very unlikely. But all the same, it does carry (trace?) amounts of nicotine and those flavourings.
Funnily enough, the biggest health risk may be in the flavourings since nicotine in second-hand amounts is likely to have no effect whatsoever. The food-grade flavourings we're inhaling though have never been studied as safe for inhaling which is why more studies (
like the current one Dr. Farsalinos is preparing) are necessary.
As a group, it's better for us to accept that this isn't just water vapour - there's already been plenty of (shoddy) press coverage demonizing vaping - if the FDA is saying e-cigs emit chemicals and you tell people it's just water, who do you think they're going to believe? If you tell people what the chemicals are, and why then at least they'll realise you know what you're talking about.
And yes, it's ridiculous - but it's also their right to make that choice - and I'd rather they
choose to exclude vaping from their establishment (even if it's based on misconceptions) than have the government make that choice for them. Seriously - read up on the research, and if there's a local bar or pub you like that you'd like to vape in, go see the manager and educate them - whilst you still can, because at some point in the future their right to make their own decision may be taken away from them.