That has happened, but other things have also happened and been labeled this.

Part of the reason why the naive approach doesn't work is that both sides have discovered that a more pleasing way to deal with disagreement than to say "here, let me show you!" is to misrepresent and belittle the other.

It's less a case of "evidence be damned" and more a case of "why do I change my mind believe this claim from that other hostile side when it too is only backed up by invective and structured as propaganda?"

The problem is that without persuasion, your only tools are manipulation and oppression. You ask for it yourself: a competing propaganda arm, which pretty much by definition can only lie to people. Noble intentions, perhaps, Saruman, but wielding the Ring can lead only to evil.

We tell the fairy-tale version for the same reason our fairy-tale heroes are morally upright or at least morally redeemable: it's not because people always are, but because this is what we aspire to, and for good reason.

So I think the fairy-tales are fine. Rather than dragging our fantasy into the mud, I think we should endeavor to grasp more of the fantastic behavior in the real world, at least by being perpetually open to it happening instead of labeling those with a different perspective as enemies and tarballing them until they wouldn't take your statements seriously if you descended from heaven in a column of sparkling light.