I’ve never been a smoker, but I would oppose that ban. Blowing vapour around is what we all do when we breathe, and the rapidly dissipating visible “smoke” from these cigarettes is probably the part we have to worry about the least of all the products of “second hand breath”.
As for the concentrated fluid, there are a lot of substances that adults deal with that could be dangerous to kids if used in the wrong way. Don’t leave dangerous stuff lying around, whether it’s bleach or e-cig fluid.
My only real objection to using e-cigs in public is that they look like normal cigarettes and I’d rather not water down the social opposition to smoking around non-smokers, especially children. There’s also the idea that children could see smoking as cool based on this, or think of e-cigs as harmless because they’re used in public without any objections. I don’t see a lot of evidence for this though; on the contrary, I see e-cig smokers as people who are trying to take control of their lives in an area that is famously difficult to control, so I would support them and explain that to my kids if they saw someone “smoking” in the same room.