My opinion is that he's a loving son who's not going to say Dad's a fruitbat. But who knows what his real opinion is. I tend not to believe what alcoholics say when drunk. I learned that first hand.
In an interview a few years ago, when he was asked about his father, he got a bit testy and said "do not ask me about my father" or words to that effect. He did not disown his father's opinions in any way...