Regardless of your profession or trade or hobby, there is always some benefit in joining an association . It demonstrates unity. It brings knowledgeable people together to address common issues. It provides a forum for an exchange of ideas within the community. It gives you access to the experience and knowledge of others.
If you don't wish to join the AMA, thats your choice. It sounds as if you don't actually need the AMA to fly at your location. But the AMA is the unified front needed for us to pull together when issues threaten the hobby, like fighting for our share of the band width , as an example. When I balance the accomplishments of the national organization against the bad behavior of a handful of its members, I choose to support the AMA.

Now, if you let the *****holes keep you from joining, what happens ? The *****hole quotient goes up. Pretty soon, all we have is *****holes. We need good people. We need you. The solution is dilution.