To be fair, Orwell writes in Homage to Catalonia that even though he fought alongside Communists, he was there to fight against fascism, not for communism. I think it makes sense that the communists are not all that eager to praise him; that they are too ignorant to read him is their loss.
No matter how you put it, Stalin was certainly a more effective anti-Communist!
True, I always read him as at least sympathetic to the original communist struggle, no matter how much he despised Stalinism and authoritarianism.
It does, however, make sense that people who in all likelihood consider themselves Stalinists wouldn't be the biggest fans of Orwell. What doesn't make sense is that these morons still exist at all, but that's a different issue entirely.