Nazis built 6 extermination camps in Europe, all on Polish territory. We know whose best ally Poland is. And when the Holocaust was over in 1945, the only large Jewish pogrom took place in Poland, in 1946.
Nazi concentration camps were built on the Polish territory at the time when it was occupied by Nazi Germany.
This narrative advances hate speech and historical revisionism - tactics commonly used by pro-Kremlin outlets. It also uses anti-Semitism - another recurring narrative of pro-Kremlin outlets, applied in reference to the US, Poland, Ukraine and others.
EUvsDisinfo recorded many examples of how anti-Semitic claims are used by pro-Kremlin media, see a few examples here: