You could throw a bit of “sunk cost fallacy” in there (he bought an anti-dragon whistle, he’s spending his time and energy blowing it),

And popularity bias (if anti-dragon whistles are popular)

And convention bias too of course (everybody knows that anti-dragon whistles keep dragons away. It’s right there in the name).

And authoritarian bias (if the authorities are recommending anti-dragon whistles)

Also, any evidence-based assertion-maker could be accused of making his assertion on insufficient evidence. Which might be the case here. But as opposed to what?

Hmm. What else? Specious reasoning?

But what we want is examples. Speak to me, awakened ones. Tell me what fools these sheeples are.