I had the same question opening this thread so I googled it.

the interconnected nature of social categorizations such as race, class, and gender as they apply to a given individual or group, regarded as creating overlapping and interdependent systems of discrimination or disadvantage.

I googled it after reading your comment cause I realized I didn’t actually know what it meant.

There were a few definitions but I’m guessing this is the one the person you’re replying to meant:

“deliberately attempt to conceal unpleasant or incriminating facts about (someone or something).”

Idk why they thought someone calling out Nazis for spending resources on the Holocaust up until the very end meant that people are whitewashing Nazis though.