George Orwell was a lifelong socialist who never shied away from criticizing fellow socialists, but he fought as an armed revolutionary in the Workers' Party of Marxist Unification (that's where he was shot through the neck by a sniper). He wore the insignia of the hammer and sickle. You can read all about it in Homage to Catalonia.
The idea that he was anti-Communist comes from his anti-Stalinism, after he saw the Left split by authoritarian factions. 1984 represented his fears that Socialism in the West could be corrupted by personality cults and led into the same pit Stalin took the USSR.