And then both of them end up marching angrily away and thinking that the other person is a complete idiot.
And in this case, the layman is much closer to the truth. While the scientist in question likely isn't an idiot, he is basically a liar.
For the scenario indicated, “there’s no scientific evidence for X” - is almost always false. The "scientist" in question is arguing from authority with a lie. He doesn't have fantastical standards for evidence, he just pretends to himself that such standards are appropriate for things he disagrees with.
If the scientist actually says
“Well, there might be something to it, but the successes that you mention could very well just be coincidence, and it’s really really hard to figure out whether that thing actually works, even if we do lots of careful experiments. So although the thing that you mention could be worth looking into, we really don’t know whether it works yet, and most things like that actually turn out not to work when you do the experiments, so for now we should assume that it won’t work.”
possibly starting with "Maybe, but I have heard ...
Paper by the Cultural Cognition Project: The culturally polarizing effect of the "anti-science trope" on vaccine risk perceptions
This is a great paper (indeed, I think many at LW would find the whole site enjoyable). I'll try to summarize it here.
Background: The pro/anti vaccine debate has been hot recently. Many pro-vaccine people often say, "The science is strong, the benefits are obvious, the risks are negligible; if you're anti-vaccine then you're anti-science".
Methods: They showed experimental subjects an article basically saying the above.
Results: When reading such an article, a large number of people did not trust vaccines more, but rather, trusted the American Academy of Pediatrics less.
My thoughts: I will strive to avoid labeling anybody as being "anti-science" or "simply or willfully ignorant of current research", etc., even when speaking of hypothetical 3rd parties on my facebook wall. This holds for evolution, global warming, vaccines, etc.
///
Also included in the article: references to other research that shows that evolution and global warming debates have already polarized people into distrusting scientists, and evidence that people are not yet polarized over the vaccine issue.
If you intend to read the article yourself: I found it difficult to understand how the authors divided participants into the 4 quadrants (α, ß, etc.) I will quote my friend, who explained it for me:
I was helped by following the link to where they first introduce that model.
The people in the top left (α) worry about risks to public safety, such as global warming. The people in the bottom right (δ) worry about socially deviant behaviors, such as could be caused by the legalization of marijuana.
People in the top right (β) worry about both public safety risks and deviant behaviors, and people in the bottom left (γ) don't really worry about either.