Lies are harmful

What about the fact that the child simply needs to learn to distinguish between things like truth/exaggeration/fantasy/actor play/hypothesis/trick/trolling/manipulation/sophism/misch? And learn an adequate response for each of these cases?

That then he would not spell with the foam in his mouth, that "in the movie all lies are not so!"and "in the news said - that is, the truth!".

If you deprive him of such innocent reality assessment trainers, like Santa Claus, tooth fairy and magical fairy tales, then we get a world divider in black and white.