"someone claimed Jews X" is pretty much the standard of evidence the Germans used (I know you don't mean it this way of course)
And if Hitler did it it must be bad! (On the subject of 'standard of evidence'...)
Well aware of the Hitler fallacy, it's quite common among (us) Jews. "Someone said Y X" is still a shitty standard of evidence to begin with. Considering that people are not emotionally neutral to Jews in general hearsay is even worse. In this case the undercurrent of meaning is quite possibly "greedy Jews woud rather die than part with their pianos". I suspect that Daniel is too refined of a person to catch that; it's still not epistemically hygienic.
I'm looking for historical examples of "flinching away," so I can illustrate the concept to others and talk about motivated cognition and leaving a line of retreat and so on.
The ideal example would be one of motivated skepticism with grave consequences. Like, a military commander who shied away from believing certain reports because they implied something huge and scary was about to happen, and then the huge and scary thing happened and caused great damage. Something like that.
What examples can you think of?