It’s just lousy education, OP.

Generic anticommunists acknowledge that the Shoah happened based on substandard education, not by trying to examine all of the overwhelming evidence for it. Consider Denying History: Who Says the Holocaust Never Happened and Why Do They Say It?: aside from showing how Shoah deniers operate (sometimes elevating their deception to the level of a business), it shows that we have plenty of good reasons to consider the Shoah factual, such as hundreds of documents authored by all sorts of people, photographs taken by all sorts of people, camps that we can still visit, inferential evidence (population demographics), proof of intent (e.g. the Wannsee Conference) and eyewitness testimony from a huge variety of people, from ordinary survivors to Sonderkommandos to SS guards to commandants to local townsfolk and even to high‐ranking Axis officials.

By contrast, accusations like the famine–genocide conspiracy theory are based almost entirely on guesswork (similarly to how prosecutors successfully convicted Clayton Johnson of uxoricide), and other accusations like the Uygur genocide conspiracy theory involve a small amount of uncompelling evidence, like umpteen actors eyewitnesses who are coincidentally all tied to a D.C. organization, or several photos that look kinda suspicious, a few confusing videos free of context, and a cultist who pretends to be an expert on the subject. When you compare the Shoah’s overwhelming evidence to the piss-poor evidence for anticommunists’ conspiracy theories, the differences are stark indeed.

Anticommunists who explode at us for not immediately accepting their canards at face-value should not hesitate to believe that the Czechs were committing atrocities against Germans.