Although, I am unopposed to retaining or changing the class rule, I understand your position. That said, I would still encourage you to contribute to the class. Your voice will speak louder as a member - if you believe that rule change is that important, then advocate for it.
It is important to keep in mind that the J/30 Class
Association does more than simply make rules for One Design sailing. They keep the J/30 relevant as a class by organizing the annual Nationals, hosting this website (which is a tremendous resource for anyone that has an interest in the boat), encouraging local fleet activities, and providing a means to establish the class rules.
Without a National Class Association, there wouldn't be any rules to protest. If everyone abstains from membership because of a rule they (perhaps legitimately) disagree with, then there won't be a class or rules with which to disagree. We all benefit from the class whether we go to the Nationals or not; without it, we'll all have just another 25+ year old boat.
Surely that's reason enough to contribute?