Eight days of rafting down the Colorado River in the Grand Canyon with my daughter promised to be an exceptional experience. Introducing myself to a fellow voyager, a Texan, I joked that surely Texas wasn’t really planning to secede, because it would be a pain to have to obtain a visa to visit Austin. This didn’t seem to go over well. Perhaps I had overreached. I retreated for the rest of the trip into an affable neutrality. Turns out, others did the same. There would be an occasional dig at President Joe Biden’s senility or a whisper about former President Donald Trump’s criminality, but soon, a taboo began to govern the otherwise warm and caring sociability of our group. Even though we were a diverse assembly of 30 people, gay and straight, black and white, ages 9 to 81, a freewheeling dialogue about politics or religion in the group at large was strictly off the conversational table. In spite of us all being citizens of one country, float...