Lol no. As a local, I can attest that San Francisco is vastly diverse with regard to religion. Catholicism is more predominant in its presence than Protestantism on top of that. You should visit Grace Cathedral and a number of the more prominent churches to see firsthand about what I'm talking about. But really, from Hinduism, Islam, Taoism, Buddhism, Catholicism, Judaism, Protestantism and yes, Scientology; San Francisco is a very religiously syncretic city.