Mr. Berg just had a lesson in reality, and he doesn't like it. Giving aid and comfort to the enemy has unpleasant consequences. He's a sixties idiot. He'll never face the fact that he played a big part in his son's brutal murder, and every time he appears in public, he makes a bigger fool of himself.
Yes, I think that's true. I also thought Daddy Berg's activities are based on the principle that the best defense is a good offense. I don't think Nick Berg was intentionally doing anything sneaky, but I'm sure his father probably was, or at least was involved with people who were. I am sure they were using Nick Berg, who sounds like one of the world's most well-intentioned and gullible people, unfortunately.
I don't think Daddy wants to be investigated, and he's attacking publicly to forestall this possibility. And I agree, I think he's very much aware of his guilt in his son's death.