Re "I agree that strident isn't quite the right word, but I wouldn't compare them to Muslim extremists.":
I think what turns someone into a fanatic is when their sense of identity becomes centred on their beliefs. Once that happens they experience any challenge to their beliefs as a personal assault and go into irrational retaliatory mode. Avoid all "isms" and "ologies", say I. The Zen writer R H Blyth was once asked by a friend who was considering joining the Catholic Church if he approved. Blyth replied: "Never join anything you're going to have to defend." Wise words.
