I'm on your side of the argument but I have to point out he could be referring to the Katyn massacre by the NKVD, where thousands of the most educated Poles - officers, doctors, etc. - were rounded up, and executed many with a bullet to the back of the head.  (Although I believe, many more were put out on barges then sunk).

The Soviets blamed this crime on the Germans for decades, and many Poles have not forgiven "Russia" for this national catastrophe.   Nor has Russia properly apologized or taken responsibly for this, or any of their atrocities against Poland in WWII.    Just trying to shed some light on Poland's seemingly pro-banderite stance, but not justify it in any way.