Really, I think anyone considering themselves a Leftist needs to read False Witnesses and Masses, Elites, and Rebels: The Theory of "Brainwashing." Both are excellent examples of why people don't change their minds when seeing indisputable evidence, they willingly go along with narratives that they find more comfortable. It explains the outright anger liberals express when anticommunism is debunked. That doesn't mean Communists don't do the same thing, but as we live in a liberal dominated west (most likely, assuming demographics) this happens to a much lesser extent because liberalism is that which supplies these "licenses" to go along, while Communism requires hard work to begin to accept. This explains the mountains of sources Communists keep on hand, and the lack thereof from liberals who argue from happenstance and vibes.