"I wouldn't like you to judge your father on what you saw there, Harry. He was only fifteen -" (Harry Potter and the Order of the Pheonix)
"Don't give me that!" Harry shouted angrily. "I was eleven when I risked expulsion to help Hagrid out with his illegal dragon. I was eleven when I led my friends into danger and I was eleven when we had to leave a friend behind when we thought he had sacrificed himself. I was eleven when I risked my life to stop Voldemort from getting the stone.
"I was twelve when the entire school turned on me, thinking I was the heir of Slytherin. I was twelve when my best friend was petrified and I couldn't do anything to help her. I was twelve when I led my best friend into the Chamber of Secrets to save his sister's life. I was twelve when I ended up having to go in alone and face Voldemort again and I was twelve when I fought a basilisk. I was twelve when despite the poison flowing through my veins I still managed to destroy the diary that was giving Riddle form and save Ginny's life.
"I was thirteen when I had a crazed mass murderer after me. I was thirteen when I found out that that murderer had been my parents' best friends, that he was my godfather. I was thirteen when I confronted that murderer and I was thirteen when I chose to let him live, when I gave him a chance to explain himself. I was thirteen when I found my parents' real betrayer and I was thirteen when I stopped his friends from killing him. I was thirteen when I faced hundreds of dementors twice in order to save my friend and godfather from having their souls stolen. I was thirteen when I helped my godfather escape from the Ministry and find somewhere to hide.
"I was fourteen when I was forced into a tournament that I wanted no part in. I was fourteen when I was made to fight dragons and merpeople. I was fourteen when I was told that I should abandon the rest of the hostages at the bottom of the lake when I had absolutely no way of knowing whether they would be safe and I was fourteen when I made the choice to stay and make sure they would all be rescued. I was fourteen when Cedric was murdered in front of me. I was fourteen when I was forced to be a part of Voldemort's rebirth. I was fourteen when Voldemort tortured me with the Cruciatus curse. I was fourteen when Voldemort made me fight for my life. I was fourteen when the Minister accused me of lying and branded me a crazed liar that would do anything for attention.
"I was fifteen when I saved my cousin from the dementor despite the fact that he has tormented me all my life. I was fifteen when my teacher decided to torture me into silence. I was fifteen when I decided that if nobody else was going to do anything to help prepare the students for the real world that I would. I was fifteen when I decided to speak out and tell the world the truth about Cedric's death.
"Don't you dare tell me that being fifteen is an excuse for being cruel. You don't have any idea what it is like to be humiliated in front of everyone do you? If you did you could never act the way you did. I think Snape has every right to hate the lot of you for what you did to him. You have no one but yourself to blame for the way he acts now. I'm disgusted with you. And how could you lie to me? You told me my dad was a good person!"
At this Sirius cut him off, "He was Harry—"
"A bully is not a good person! All my life growing up, there was never anything I hated more than a bully. If this is what you were like than I guess I'm better off not having known my father!" Harry declared to the others' astonishment.
"Harry you can't mean that!" Remus exclaimed shocked.
"The hell I can't. I don't want to talk to the two of you anymore. I have to go. Leave me alone for now, I need time to acknowledge what this means and I really need to think on what else you may have lied to me about."
And with that Harry turned away, left the fire and walked out of there lives.