Disavow his father's remarks about Jews, for starters.
Remember his "My father never told me a lie" in the Diane Sawyer interview?
If he still believes that, then he's as racist as his dad.
Which, considering his father is a raving Holocaust denier, is an interesting comment.
Do you really expect him to call his Dad a liar?
From a link you posted.
When asked by an interviewer in early 2004 whether the Holocaust happened, the actor / director / producer responded that some of his best friends ''have numbers on their arms,'' then added: ''Yes, of course. Atrocities happened. War is horrible. The Second World War killed tens of millions of people. Some of them were Jews in concentration camps.''
That quote is taken out of context. The question was about Hutton Gibson's view of the Catholic faith. It was not about Hutton Gibson's view of Jews. Gibson was remarking that his father had taught him the faith not that his father had taught him about Jewish conspiracies.