Most of us are aware he's a Catholic traditionalist. If you google "Hutton Gibson" you find more. You find that he's written books with titles like, The Enemy is Here! and Is the Pope Catholic? and writes (or used to) a newsletter called The War is Now!
He's hardcore - a sedevacanist who believes that Lefebvre was a heretic.
I have no doubt that in the reams of material he's published, the media can easily find opinions of the father's that they hope will reflect badly on the son.
BTW, you may now that Hutton Gibson moved his family from NY to Austrailia in 1968 - did you know he used $25,000 he won on Jeopardy to do it? I didn't.