In 1984 what causes people to be so sadistic, and why is Winston different?

Most people in Oceania have been cultivated to feel hatred by the propaganda to which they are subjected nearly every waking moment. Because the Party regulates everything people hear or read, they hear no dissenting voices. The miserableness to which they have become accustomed makes them weak and fearful, so they desperately look to the Party for guidance. They are too worn out to recognize that they are being taken advantage of by the very government they think will save them from harm; they are deceived into thinking the Party will supply all of their needs. The people of Oceania are sadistic in part because they have been taught that a foreign enemy is always attacking them. In response to their fear, they vilify anyone they perceive as unsettling the order to which they have become accustomed. Somehow Winston, perhaps because he had a loving mother and has vague memories of a time that was more pleasant than life under Big Brother, keeps thinking outside the box. He keeps asking questions, if only of himself, and he believes that life could be better. It is true that, at one point, he callously kicks a severed hand into the street. But he later identifies that action as cruel and expresses regret for having done it, showing that he is different from most other people in Oceania.