It is not such a banality, believe me.
OK, I need to clarify my "It will take many generations to get Katyn out of Polish DNA." Here is a more complete version:
It will take many generations to get Katyn out of Polish DNA to the point where the relationship between Poland and Russia would be no worse than between Poland and Germany.
You are correct in objecting to the original. BTW, the criminality of NKVD, UB, and SB was never in dispute. What is puzzling to me is that Poland didn't execute its own criminals after 1990. It seems that no country ever does, with Romania being a noble exception.