You probably don't like Severus Snape because he was mean to Harry and other students. But he has suffered. He was bullied when he was at school. He shouldn't be mean to students, but he has been deeply hurt by Harry's father, James. Also, in the Prisoner of Azkaban film, when he saw the werewolf, he shoved Harry, Ron, and Hermione behind him, to protect them. He also ended up liking Harry in the end. How can you blame him now?