This is a device that was designed to emit toxic vapours.
Nicotine may be a toxin, but in the amounts in which it's consumed, that's the least concern about the effects upon the body. However, these devices weren't intended to emit other toxic vapors.
It's like saying that fireplaces pose a fire hazard or that an electric outlet carries the risk of electrocution. It's what it's supposed to do.
False. A fire hazard is an uncontrolled fire. A fireplace is designed to control a fire. An electric outlet is not designed to electrocute you. It's designed to deliver power to an appliance. Granted, some of them are not very well designed to explicitly not electrocute you, but that's a separate issue.
The idea of the vaporizer is to deliver as clean a smoking experience as possible. If you put water-based herbal extracts into them, that's what you're doing. What's interesting is that these other things aren't that clean, either. Anyone remember transparent cigarette papers? They were everywhere for a while, I went through a couple of packs myself on the basis that I was already smoking tobacco so who cares, but what was found is that only the center of the cherry is hot enough to burn the combustion byproducts into something harmless, which meant that you were getting a bunch of toxics from them even worse than smoking paper.