Often people can only take so much pressure before they seek to release it in rash and sudden ways, throwing caution and a careful consideration of consequences to the wind. There were good signs when President Trump was elected that many Americans were entering into that kind of moment. And now, with millions realizing just how widespread and deeply rooted are the problems cool-and-collected President Obama had helped us emotionally paper over, the urge to find release in rash words and deeds is kicking into overdrive. There’s talk of a “cold civil war,” a bitter longing for “national divorce,” and...