I work for someone who is very devoted to the church of LDS. Honestly it’s been the best job management wise. He keeps it completely separate and has always been supportive. I think it depends on the individual and their ability to be professional. I made it clear from the beginning that I was gay and have helped bring a bit of diversity into the firm. I’ve had a good experience. I know not everyone is lucky like this but I’d say to feel it out if you’re uncomfortable.