I think there are limits to how good one's values can get without facing one's past sins.

I don't think this is true, or at least I don't think it's obvious. When opinions change in Democratic societies, in my experience the generic stance is "That's how I always felt, I'm glad everyone else caught up." But clearly _someone_ must have changed their mind about gay marriage between 2005 and 2015. I don't think there's a limit on how far you can shift without penitence. I'm not sure that's how human psychology works.