I recall seeing that Kibbud Hatorah takes precedence over Kibbud Av. Does it? If one's father openly denigrates the Torah is it acceptable to chastise him & if the comment is made in front of ppl can one respond on the spot, publicly?
If he sees his father violate Torah law, he should not tell him: 'Father, you transgressed Torah law.' Instead, he should tell him: 'Father, is not such-and-such written in the Torah?', as if he is asking him, rather than warning him.
This is even more true in front of other people (see e.g., here).