I was a drunk for a number of years. It was in a high school context and it never translated into adulthood because I got saved and freed up from the alcoholic life... so I do have some empathy for Mr. Mel.
I feel even worse because of his very very publicly professed faith. To admit that he's an alcoholic, is a hard one to admit (although clearly he has no choice at this point). I've found that situations like these where, as a known Christian, and we publiclyly fail... it can be even MORE of an opportunity to share the love of God with the world.
The world looks at us as people who are trying to be perfect and we can come across as pompous. It's not even necessarily our fault, but it's a by-product of trying to live a Holy life. But admitting to the world that the only real difference is that we are accepting the forgiveness that Jesus brings, paving the way to have the FREEDOM TO CHOOSE not to sin, it actually shows us as human... and it can be a "common ground" moment with others.
I feel bad for Mel, but at all times when you are walking with Jesus, your life a process that God uses for His Glory, His Name and His Renown. He's no respecter of persons and that includes Mel Gibson. He's a lump of clay that God is molding... and I suspect that God has a larger plan for Mel because of it.