It's like China is just that one country (aside from the Khmer Rouge) that every ML (aside from Dengists like us) agrees to hate on.
Fellow Traveler and leftypol uploaded videos criticizing them, the Shining Path hung up literal dogs to protest them, Maoists go all insane saying that it's some red fash social-imperialist nation because (insert nato propaganda here). And Hoxhaists claim that China was never socialist and that the only socialist nation ever was USSR before Khrushchev and almighty holy Albania.
What is it that makes China so controversial even among MLs? I get that it's not perfect and every AES state has their Ls, but jesus.
Propaganda is helluva drug. I believe there's so many layers of brainwash to clean off before most people see the cracks behind CIA lies of China. Though I think people can skip this process of unlearning if they visited China, watch videos of people having a good time in China (and what an absolutely beautiful, majestic country it is, looking like something from a science fiction/fantasy with so many wholesome and wonderful people), or read a non-Western book about China. When I began reading Socialist Reconstruction, my wife was skeptical of how China was being portrayed very positively, but I was slightly more willing to accept the book as being truthful and not "overly-biased" (not that I care about bias, as long as the message is honest). Only recently after, my wife and I began freeing our Western conditioned minds.
I believe people like Fellow Traveler and such should know better by now. Maybe they are being used as controlled opposition, idk.
I definitely agree it would help if these people would visit and see for themselves. However, I think the propaganda point is more complicated than you portray. Many people are convinced US enemies are bad, not because primarily because they are tricked, but because it makes them feel better. They can feel better about their own circumstances in the west if they can say "at least I'm not in (insert enemy country)." This works in a peculiar way on the western left where it may work for them to think "It's not our fault that we aren't anywhere near socialism. It's all China/Deng's fault for betraying the revolution and bringing new life to capitalism. Now all the real socialism is on it's back foot." Those that aren't total doomers from that thinking may add "maybe we could have an international revolution liberating us and the Chinese people from their chains." This all ties in with the martyr fetish thing.
Another dynamic is contrarianism. Communists don't want to believe the CIA/news/etc. The news says China's an authoritarian socialist hellscape. The western Communist is confused. Are they good but not socialist? Are they still authoritarian but not socialist? Then they think of the other things mentioned in this thread or remember Lenin's approach to the international situation around WWI and conclude China's a rival imperialist. "China's obviously doing capitalism so well that they are beating the old imperialists. They claim it's socialist and uphold Mao in words because people know socialism is good." This totally makes sense if you don't engage in Chinese theory. It also makes sense when some of China's most ardent English language supporters are clear revisionists. I'm speaking of the "Patriotic Socialists" and those like Micheal Hudson.