Tuiaki did over his time as BYU DC, he said it was good for both sides to move on.
Look, I'm of the opinion that it wasn't just the last two years that the defense was bad. But there's no use kicking the guy in the rear on his way out. Thank him for what he's done (even if the thanks aren't entirely genuine) in his time here and move on. Tuiaki is a good man. It's also ok to admit that it's time for change.