JFK in fact disavowed his father's views, in his writings (While England Slept) in his deeds, (going off to the war Joe Kennedy did not support) and in his words. In fact it could be argued JFK made his political bones by opposing his father's WWII isolationism. And nobody ever thought he loved his father any less.
I think it was absolutely fair game to expose the views of Hutton Gibson. Mel is a public person, from that flows all his power, and he had to know his father's views would come out. Under the circumstances his father's views are germaine. Nor did Gibson do much to muzzle his father, which in itself gives me pause. I have not seen the movie, so I can't say yea or nay on that matter, but I long ago made an educated guess about Mel Gibson, vis a vis anti-semitism.
Who could muzzle their own father?
If I had tried to muzzle my father, I'd have gotten exactly the opposite result.
Educating yourself from faulty sources does not an educated guess form.
Gibson has stated flatly that his views are not his father's. He is not an anti-semite by any stretch of the imagination. But some here might be anti-catholic.
I say "might be".