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 too many enthusiastic claims that failed later so I'm skeptical.", then it is no lie and both don't need to depart angrily.

But a condescending "science says no" surely sounds like ivory tower arrogance.