Hmmmm ...
Mr. Galelao, you can read an astronomy book and see that throughout history the sun has always been and continues to be defined as revolving around the earth.
Mr. Darwin, you can read the Bible and see that throughout history that the origin of the species has always been and continues to be defined as created by God in 7 days. (Okay, so maybe not such a good example.
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There are so many other ways to take this - a woman's right to own property, vote, equal pay, control of her own body (and if you think the only thing I'm talking about is abortion, you should have flunked history); the treatment of mental health conditions as something other than demonic possession, or medical care with some compassion; the rights of African-Americans to the protections of basic citizenship (and, for that matter, it's only been a few years since Jews, Eastern, and Southern Europeans were considered "white.); there are just too many to mention.
And gay rights, including marriage, like the examples I used above or so many more, is just one more thing that the ignorant, the bigoted, and the small-minded are bound and determined to fight.