No I don't see why it would. I would say authors of fiction genres such as erotica and gay fiction have it harder than anyone when it comes to promote. I don't know much about Christian non-fiction, but the Christian Fiction authors I know of seem to do pretty well with promotion so I haven't seen any differences. I'd think of all the religions, writing a book about Christians would be more accepted than an athiest writing about atheism or someone writing about being a muslim to some people.