But this is why e-cigarette campaigners say that politicians are just meddling out of personal distaste, rather than any scientific backing. The two core reasons why cigarettes cannot be smoked indoors are:
1) Doing so (potentially) causes deleterious effects to people who inhale the second-hand smoke. At the very least, it can be agreed that it's not preferable to breathe smoke.
2) It makes it likelier that the smoker will give up their dangerous addiction.
Neither case can be particularly easily applied to e-cigarettes, which emit harmless water vapour, and are to many smokers a means of giving up their dangerous smoking addiction.
I must say I agree with the e-cigarette campaigners that attempts to apply the same laws to e-cigarettes as cigarettes is just yet another example of politicians wanting to control something absent of any scientific proof that they need to do so.