Safer according to what study? People just assume they are safer.
Also, without direct evidence or rigorous analysis it would still be preposterous that a mixture of nicotine, fragrances, propylene glycol, and vegetable glycerine would be anywhere near as harmful to the lungs as cigarette smoke. There is a difference between "just assuming" and applying common sense.
But a million anti-smoking advocates don't give a shit.
Not all side effects are caused by the active ingredient.
If the ecig industry were regulated, then we could make sure the liquid has no or minimal side effects.
In my country it is worse because ecigs are forbidden (given that uncertainity), so we have a black market for ecigs, making the quality of the liquids even more quetionable.
I know tobacco is really bad, and I have doubts about ecig. So, I give the benefit of the doubt, as it is little probability it is worse.
I'd actually be more concerned about the hardware than the liquid. It would be easy to cut costs by using unsafe materials for heating elements, solder, or the wicks. But even with all of that risk, you're going to have a hell of a time beating the harm of cigarettes.