Is religious affiliation a better indicator of bigotry levels than any other factor?

I think it can be. As an Episcopalian I can tell you that most of the people in my church are wonderful, open, accepting people. However, I know a few who are rather closed-minded. When someone mentions Quakers, Buddhists, or Unitarians, I think of people who are accepting and open. I know some Methodists. Some of them are quite tolerant, but some are not. I don't really know any Baptists or Pentecostals very well, but I don't get very good vibes from them. But, I do think it does depend upon the individual person in some cases.