If same-sex marriage is used to pummel religious Americans into submission, it will be a disaster. I’ve supported same-sex marriage ever since I first heard the idea. And when I became a political columnist in the early 2000s—despite being the “conservative” at a good-sized newspaper—I was the only one at the paper (as far as I can recall) who unequivocally backed gay marriage publicly. Though I wasn’t gullible enough to believe I’d be persuading many readers, I was gullible enough to believe that my allies in the cause were merely concerned with “equality.” As we dig out from the avalanche...