"Mrs. Parsons would be vaporized. Symes would be vaporized. The girl at the next table had turned partly around and was looking at him. A sweat started out on Winston's backbone. A horrible pang of terror went through him. Why was she watching him?" (61)
"For whom, it suddenly occurred to him to wonder, was he writing this diary. For the future, for the unborn. For the first time the magnitude of what he had undertaken came home to him. How could you communicate with the future?" (7)
"He would flog her to death with a rubber truncheon. He would tie her naked to a stake and shoot her full of arrows like Saint Sebastian. He would ravish her and cut her throat at the moment of climax." (15)
Winston makes a habit of imagining who will be vaporized and who will not, a violent, paranoid, fantasy that he can't stop. Once the girl looked at him, he had a physically anxious reaction and his thoughts spiraled into the worst case scenario of her being a spy. He is caught in his paranoia as the regime has taught him to be and he is both product and victim simultaneously.
Despite Winston's steadfast fear and hate (equal in measure) towards the Big Brother regime, he wavers in his act of rebellion multiple times, down to its very foundation of purpose. What is the point of his communication? Who could listen? What would this change? His pessimism is a motivating force for him, regardless of whether it moves him backwards or forwards, it does move him all the same.
Winston is beyond just violent here. He's predatory, blasphemous, jealous, and indulgent. Predatory because he focuses on the youthfulness of the girl and the forbidden fruit of her celibacy. Blasphemous that he invokes the name of a saint, jealous as he acknowledges that he can't have her but wants to, and indulgent in that the entire spiel is a part of The Two Minute Hate, the only time he can be negative so he is gluttonous with permission.