Here are some of the reasons why Snape is not bad in the Half-Blood Prince:
- He saves Harry's life on several occasions, including when he stops Draco Malfoy from killing him and when he provides him with the antidote to Voldemort's poison.
- He teaches Harry Occlumency, which helps him to protect his mind from Voldemort's Legilimency.
- He provides Harry with valuable information about Voldemort's Horcruxes, which are essential to his quest to defeat him.
- He ultimately sacrifices himself to protect Harry and ensure his victory over Voldemort.
While Snape may have a complex and sometimes dark personality, he is not ultimately a bad person. He is loyal to Dumbledore and the Order of the Phoenix, and he is willing to do whatever it takes to protect Harry and defeat Voldemort.