> In the absence of more reliable indicators

This is half the answer, though we'd also need those indicators to be plentiful and compelling.

> we know very well how personal behavior is distorted

This points to the other half: humans are irrational by default. We tend to believe what we "experience" - see, hear, etc. - even if we know it's a lie. Have you seen those videos of people in VR glasses panicking as if they're about to die because they've just fallen off a virtual cliff?

Consider also the Illusory Consensus Effect: mere repetition of information increases the estimates of group members that other group members believe or already know that information. Logically redundant, rhetorically effective.

We're apes with a souped up prefrontal cortex - critical thinking is expensive so applied selectively (see Tversky and Kahneman, System 1 vs System 2 thinking).