"To make the cauldrons explode and others look bad." Harry said, being careful to leave out names. "Sometimes children think things are funny that really aren't."
Keeping his eyes on Faustus's face Harry waited as he appraised him. He could see from the corner of his eye the sardonic look on Severus's face, he was on his own with Faustus's question. Pausing as he tried to formulate his answer Harry finally said. "I think a large part of it was we didn't really know each other. Since we didn't know each other we reacted badly to things that each of us did."
Trying to say this without saying Severus had been an arse and judged him based on his father's actions for years was hard. Though it hadn't helped that Harry had gone out of his way to prove him right for years. "Your father and I have had many roles to play over the years. Some of those roles didn't make it possible for us to get to know each other and stop fighting for a very long time."