From the New Yorker's tediously fact-checked, litigation-proofed article on Scientology by Laurence Wright:
On August 19, 2009, Tommy Davis, the chief spokesperson for the Church of Scientology International, received a letter from the film director and screenwriter Paul Haggis. “For ten months now I have been writing to ask you to make a public statement denouncing the actions of the Church of Scientology of San Diego,” Haggis wrote. Before the 2008 elections, a staff member at Scientology’s San Diego church had signed its name to an online petition supporting Proposition 8, which asserted that the State of California should sanction marriage only “between a man and a woman.” The proposition passed. As Haggis saw it, the San Diego church’s “public sponsorship of Proposition 8, which succeeded in taking away the civil rights of gay and lesbian citizens of California—rights that were granted them by the Supreme Court of our state—is a stain on the integrity of our organization and a stain on us personally. Our public association with that hate-filled legislation shames us.” Haggis wrote, “Silence is consent, Tommy. I refuse to consent.” He concluded, “I hereby resign my membership in the Church of Scientology.”Haggis was prominent in both Scientology and Hollywood, two communities that often converge. Although he is less famous than certain other Scientologists, such as Tom Cruise and John Travolta, he had been in the organization for nearly thirty-five years. Haggis wrote the screenplay for “Million Dollar Baby,” which won the Oscar for Best Picture in 2004, and he wrote and directed “Crash,” which won Best Picture the next year—the only time in Academy history that that has happened.
That's pretty funny when you think about it: a major player in Hollywood is a Scientologist for his entire career, but he finally rebels because ... one Scientologist staffer in another city signed a petition against gay marriage.
To me, the most interesting thing about Scientology is how it was an outgrowth of the Golden Age of Science Fiction. L. Ron Hubbard was a sci-fi writer, the great editor John W. Campbell heavily promoted his Dianetics (which was originally intended not as a religion but as an equally plausible and cheaper competitor for Freudianism), and Hubbard's pal Robert A. Heinlein supposedly gave him the idea that you could get rich starting your own religion.
I've wondered how often Heinlein was tempted to launch his own cult, seeing the success of lesser popular novelists like Hubbard and Ayn Rand as cult leaders. I suspect Heinlein was too easily bored for the repetition necessary.