Ok, lot of stuff to unpack here, but I'll stick to just pointing out obvious misinfo, which is often repeated:

Chomsky never backed the Khmer rouge, he questioned some of the claims and western focus on the Khmer rouge, which was ignoring US culpability. He also never denied that the Khmer rouge were committing atrocities.

Was he wrong? Yes, at least in specific instances. But he was never outright supportive of the Khmer rouge. This is very old propaganda.