Before WWII Poland was a rather xenophobic place, where people believed the Jews were drinking baby blood. You don’t see a lot of this in Poland nowadays, in Lvov at least half are still around these lines. And they managed to bring it to Kiev.
It only really happened after Piłsudski passed away in 1935, and the Endecja took over. Piłsudski was a very tolerant man.
I have heard of that, I believe it is a false construct, and it has been called “Blood Libel” and have read about it in several histories of European Nations.
I wasn’t in Poland before WWII, but I never accepted that Poland was as antisemitic as portrayed for the simple reason that so many Jewish people lived there. It isn’t logical.