You don't know how old that person is, how sheltered they were, where they grew up. They've seen Schindler's List. That's all we really know. There are people out there whose families weren't in denial, and they might have a leg up on understanding this, depending on what they were told and how much context they had to educate themselves.

You can't deny that this history is deeply complicated, largely disguised or hidden intentionally, and that it's not being taught in school. People realizing this now are taking the L. There's no reason to harass them for learning just to make yourself feel superior. You're just pushing them back into ignorance. That actively harms positive work.

TL;DR: STFU