Who said one man's terrorist is another man's revolutionary?
The book is about a British cabinet minister who is killed by an Irish Republican Army (IRA) assassin (Billy Downes), who then flees to Belfast, and an undercover agent (Harry Brown aka McEvoy) sent to track him down before he can kill again.
The book introduced the phrase, not familiar before the '80s, "One man's terrorist is another man's freedom fighter."
Many other people have quoted it too, and can be referred to the Israel/Palestine conflict, and the Iraq War, Middle East conflicts. As well as conflicts and uprisings in Africa, Colombia, etc.