I'd thank him for his honesty, tell him that I'd love to see him turn it around, and wish him luck in finding his new job if he can't get it done.
I don't hate the man, and my opinion of him would increase if I knew he had an apology like you described within him. Just as we can't blame Jay for wobbly passes and Brian for fumbles because these things are in their natures, we can't blame Wanny for not doing better. I think he took his chances with the Bears and Dolphins and he just didn't measure up. It sucks for those of us who rooted for teams he coached, but it's not like he set out to ruin our lives or anything...