Louis Theroux, the British TV host and documentary filmmaker, made a movie about the Church of Scientology without quite knowing what he was in for. His perspective as faux-naive or actually naive outsider — “I prefer actually naive,” Theroux said when I put it that way — yields a number of unexpected benefits. His Scientology movie, which is puckishly if appropriately titled “My Scientology Movie,” makes a strange, compelling and often hilarious companion piece to more straightforward investigative works like Alex Gibney and Lawrence Wright’s “Going Clear,” the Emmy-winning HBO documentary from 2015. Theroux stopped by Salon’s New York studio recently for a highly entertaining conversation about the making of “My Scientology Movie,” which to a significant degree is a movie about the making of itself. When I gently suggested that some people might call the film “meta,” Theroux embraced the term: “Yes, it is meta. That’s not a bad thing, is it?” The only possible answer to that is “It depends,” but in this case Theroux’s movie-about-a-movie captures the atmosphere of unreality that permeates …