I realize this one may be hard to swallow. It's from a wealthy, white, christian, heterosexual, Imperialist, but he wasn't ALL bad. He did write Sherlock Holmes among other things.

"I never guess. It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts."
- Sir Arthur Conan Doyle

Very appropriate advice for the "Greenies"