Explain what Winston means when he says, "They would have blown a hole in their own perfection. To die hating them, that was freedom"?

Winston fantsizes about a bullet entering the back of his head. Winston desperately resists the idea that he could succmb to party doctrin and love Big Brother. Winston imagines hating Big Brother seconds before he is killed. The party will then have lost: they would have failed to "cure" him. Winston would have found his freedom whilw the party destroyed their own perfection.