Living with his parents had been hard for Sirius even if Regulus never had a problem with them, but he could see why living with Potter's fame was a much bigger problem, although he felt that James was going at this the wrong way.
"You don't want to compare yourself to your father. Whatever he did is in the past. I'm not trying to diminish what he did, because I know what he did, but we all did something in the past. This isn't about repeating history, but planning for the future," Regulus said.
"Now, I'm assuming that you don't want to share why not your father, so instead of saying that, let Dumbledore say what he will, add your own comments, and then let your father come up with a reason why you aren't qualified," he suggested. "First, he'll have to tell you to your face that he doesn't think you can do the job. Second, he has to explain why. Third, he has to do so without sounding petty or arrogant, and trust me, your father manages to sound like an arrogant arse every time he opens his mouth... unless he's speaking to Remus apparently, but that's besides the point. Your father really comes off like a prick, make sure he does so at the meeting and you won't have to explain why you and not him. He'll show everyone why."