A rather major issue in communicating matters of science is the sentiment "that is not only not right, it is not even wrong". To be specific, it's an issue of lacking falsifiability. What this means is that for any scientific hypothesis to be worthy of any consideration, it has to be presented in a way that can be tested and includes the possibility of being shown to be wrong.
Or to put it simply, a claim can only be shown to be right if there is a way to show it is not.
Usually this issue only happens in metaphysical matters, where falsifiability is not possible by definition, but unfortunately it seems to be creeping into discussions that seem scientific on the surface. Here though, an additional layer of masquerading as science usually blurs the fallacy, by leaving out rather important bits.
Consider the following:
"Electronic cigarettes may be a gateway to tobacco use"
What does gateway even mean? Is it defined in a way that can be tested and shown wrong?
Most of the time it really cannot. The vast majority of comments including a proposed gateway-effect only mentions it's existence, without any sort of justification why it might exist, what mechanisms it contains and what would be a reasonable test to see if such an effect even exists in the first place. The comment is more or less worthless, has no real substance to consider or be concerned about. It is a legitimate question, but only in the context of actually trying to define what it means and how it might happen.
(more on this here, it's a rather complicated subject)
Then, what about this:
"Electronic cigarettes have formaldehyde in them"
Formaldehyde is infamous for being an embalming agent and a carsinogen, so this evokes fear and doubt about the safety of vaping.. But is it even wrong? Sure, it's technically falsifiable.. But the existence of anything is meaningless without comparisons.
Human breath also has formaldehyde, but that doesn't exactly tell us anything relevant. Is the amount of the substance enough to be a part of any meaningful discussion? Is there an actual hypothesis hiding in that statement? Do we gain any real information from that statement?
So let me fix it:
"Electronic cigarettes have formaldehyde in them, but mostly in amounts that are unlikely to cause any concern to users and even less to bystanders"
And now we get something that has something relevant that can be tested, analyzed and shown to be wrong. And most importantly, can actually tell us something that IS useful information.
And a bit of analytical brilliance from my beloved country, Finland (though I don't think level of absurdity can be really fixed without abolishing the limit):
"The import limit of 10ml is based on the fact that it contains a maximum of 200mg of nicotine, which is the same amount of nicotine a person gets from 200 cigarettes when smoking them"
This is about as vacuous as one can get. Comparing the nicotine content of e-liquid to nicotine yield of cigarettes and pretending that this is somehow a reasonable calculation to base restrictions on.
"Electronic cigarettes are harmless"
No, they are not. No such thing exists. In pragmatic terms, they are practically mostly harmless as far as we know, but stating that absolutely is very much absurd as it's impossible. And this gets (rightly) used against us. So:
"Electronic cigarettes are not likely to have risks on any meaningful level, which makes them harmless enough to be reasonably safe"
Unfortunately the discourse is full of these kinds of things, on both sides sometimes even.
I really wish at least the pro-vaping side would start also being pro-science as a whole.
Don't play their game. We will lose that one.