Truly can´t understand why people can´t be honest to themselves and see things for what they are.

Plus all this information about him and many others in history is publicly available.

Because commies were allowed into the "victor club" at the end of WW2 instead of being condemned like the anti-human monsters they always were in practice. The childish, fairy tale tier theory, especially its modern metastases, obviously has them as perfect beings of infinite wisdom. And since WW2 there were multiple other commie regimes with similar victim body counts in proportion to their abilities.
Besides, the number of people directly murdered is just the driest statistic. What analyses relying on mere numbers cannot really tackle are everyday indignities inflicted on the average resident. The institutionalized hypocrisy is perhaps the worst. Everyone knows the state is blatantly lying. The TV - the state TV, there can be no other - is especially brazen about it. Yet you are supposed to parrot those lies convincingly enough or you get in trouble. The commie society has lots and lots of ways to put pressure on you without even getting into open threats or involving law enforcement. This indoctrination starts before school too, with "pioneers" and their precursors.
Then there is the need to leverage connections just to procure average quality furniture, clothes and even about 3/4 of basic food. For example, you need to be "in the loop" to learn when some generally distant grocery store will have eggs on a certain day, and so you go there early in the morning to wait in line for several hours. And this little adventure has nothing on the getting actual meat quest. As opposed to tendons, other waste tissue and even hooves - those were boiled to make broth basically as there are some tiny scraps still attached to the hoof. This is just 2 somewhat important common things out of hundreds you have to learn to live with, knowing that the party basically takes a shit on you 24/7 while the highest rung is enjoying life to the fullest by hunting in natural preserves, using imported or at least highest quality domestic products which are literally impossible to procure for a mere mortal at will, benefiting from actually good healthcare in closed hospitals and resorts and so on. They live in parallel reality where they have everything and you are a serf who does not even have the right to leave, not in the least because you likely do not have a real ID but only a commie party card. Oh, you better believe you're going to become a member of the party or else.
But yeah, Pol Pot's regime is the simplest to showcase to a complete noob if you ever wondered about this. Nothing is more straightforward than piles of bodies and a broad range of torture measures for someone completely unaware of what communism really is, in practice.