I don't blame you. I feel the same way about my family. I know of other parents who play a little loose with the DF rules and my family doesn't. So, not only do they choose to follow the policy but they follow it strictly, and that's on them.
I feel pity for them in a sense, in that they let such an organization cause them to sever normal human family ties and lose out on a relationship with their son for no other reason than not agreeing on religious doctrine, but I hold them just as responsible too. Some things are just natural -like loving your family - and you shouldn't need anyone else to tell you that it's okay or not okay.