It comes down to framing. You put Animal Farm (unapologetically anti-Soviet Union) and 1984 (more broadly anti-authoritarian) on the required reading list for high schools. You haven't provided any education around Marxist theory anywhere in the curriculum besides "communism bad". That lets you transfer the idea that the USSR is representative of all leftist thought, and these books are about the USSR. Breeze over all the stuff in 1984 that points to any kind of leftist theory--which Orwell helps with because he expects people to get bored and skip that whole bit--and boom, Orwell becomes an anti-leftist icon.

If Homage to Catalonia were also added to the curriculum, this whole farce would be torn down.