Are E-cigarettes really OK to use everywhere ?

E -cigarette companies claim in their advertising,it is perfectly OK & legal to used them in public,bars,hotels and just about everywhere.
I think technically it is legal but I can see people getting up in arms and making a huge stink about it when ever they’d see anyone using an E-cigarette. What do you think ?

*My granddad had a habit of carrying an unlit cigar in his mouth all day long,many times he would end up throwing it away without ever lighting it,(“No” he would not chew on it & spit tobacco juice) You could not believe how much grief he got about it,he would get dirty looks all the time and was often reprimanded about it, a few times people would start coughing and complain the smoke was irritating them
(These people actually had red,watering eyes ??)
One lady had an asthma attack in an elevator because of the unlit cigar ?? Someone yell at my granddad & ordered him to take the cigar out of the building immediately ?