It's quite evident when you read L. Ron Hubbard's writings, particularly the older stuff like Dianetics, which says homosexuality is a serious "aberration." Hubbard despised gays. Heck, just the stereotypical gay characters in Mission Earth are so over-the-top repulsive that in itself it makes the series virtually unreadable. (It's not the books' only flaw of course—finding fault with Mission Earth is like finding hay in a haystack—but it's easily one of their most execrable features.)
I couldn't finish the first book of that series. It was terrible. Paradoxically, Battlefield Earth is one of my favorite (if not my top favorite) sci fi novels of all time. I have read a LOT of sci-fi novels, too. I didn't even know Scientology existed when I read it the first time in the mid-eighties. He wasn't pushing it in that book at all as far as I could tell.