Do you want history to teach false things according to myths?
Myths do not equal lies.
Myths are an result of focusing on positive and good facts from a collective history.
They are to provide a model for people to follow or at least to cherish.
Grown ups and educated people do realize that it all wasn't that rosy and nit. Books about that should be available for anybody willing to buy them. It doesn't mean that all failing should be a part of history curriculum
If adults are taken by surprise its their own bloody fault.
Because of their history Poles are more defensive about their past, it is understandable as for years and years the only thing they could do to defend themselves and their identity, was creating myths.
While others can always say - well, whatever, who cares? - even though those luckier nation are generally relay on myths themselves, at least general public does.
I must add that recently what can be observed in Poland (Gross and others) is not about myth busting is about creating new myths to manipulate general public in Poland into a guilt syndrome.
To hell with them and their apostles!