Your illustration of how the Jewish system was corrupt and how the prophets spoke against it and then Jesus spoke against it was awesome. Notice that they couldn't counter that. The best the one elder (Cosmo?) could do was say "Well if they ever told me to stop serving Jehovah, I would leave." Who told the people to ever stop serving Jehovah? What about in Jesus day? The only things He spoke against was the Jewish system of rules and how they corrupted the Law.
It was a rock solid argument. It was one of the only arguments that they wouldn't even touch.