Excellent! Remember your job is not to be your kids' best friend, it is to raise them to be strong adults that can care for themselves and the world they're about to inherit.
He's started an adult conversation.... keep the ball rolling. Congratulate him on the maturity it took to express that. Tell him you'll always love and accept him, period. That's immutable.
Then remind him part of being a mature young man is honoring the rights, feelings and space of those around him, just as he's expecting you to respond to, and honor his announcement. Tell him he will honor the rights, feelings and space of you and your dad, through gritted teeth if necessary. But he WILL do it. That's how grown-ups behave.
Welcome to being an adult, young man.