I am in no position to make declarative statements about what Gibson does or does not believe. Neither are you. We know what he said while drunk. We know nothing more. We can speculate, but speculation is not fact. In an attempt to visit the sins of the father upon the son, we can say factually -- as so many have today -- that his father is an anti-Semite, a bigot and a member of a strange fringe Catholic cult.
But Mel Gibson is a man who has battled alcoholism much of his adult life. Speculating now, I think he is a man at war with himself and his upbringing. If he is, indeed, an anti-Semite, does it excuse him? No, but it helps explain him.
As for me, I am less concerned about what a man says than I am about what he does. From what little I know of the man, it seems to me he's at least struggled to lead a more decent life than the overwhelming majority of Hollywood types.
"Let he who is without sin cast the first stone."