Have you ever been put off an author’s books after reading a biography of them? Or the reverse - a biography has made you love an author more?
I don't very often read biographies of authors, so the immediate answer to this would have to be no. I do sometimes try and find out a bit about an author if I've really liked a book, but only a brief overview from various online sources. I can't really imagine anything I would find out that would put me off their books.
One of the reasons I read is to get different opinions and viewpoints on the world, and maybe even expand my own views slightly. If I chose to only read authors with similar belief systems to myself, then this would leave me with a very narrow view of the world. Everyone is entitled to their own opinions and it would be a very boring world if everybody thought the same, or only read work by authors who feel the same as them, whatever the issue.
I also think that if an author's belief system is so completely opposed to mine and they choose to preach about it in a book then it wouldn't be a book I would be interested in reading anyway. If they write good books then it doesn't actually matter what they believe.
Having said all that, I now need to qualify it slightly and say that with very extreme belief systems I would refrain from buying the book. But only if I felt that my money might be going towards a cause that may actually harm people, or infringe on their rights to hold their own opinions. I think it very unlikely I would want to read a book that would fall into this category, but I wouldn't avoid it if I did. I just wouldn't buy it.
I don't think knowing information about an author would make me love them more, but it may help me appreciate their books a little more. Most authors write from experience, so it can only enhance my appreciation of the book to know even a little bit about their life.