As someone who came of age and into the peace movement during the first years of the Iraq war, I’ve been going to protests, rallies, and demonstrations—if sporadically—for nearly 15 years now. You could make a bingo card with the types you’ll encounter there… which I say in love. And if one were to make such a card, the free square is the guy with the acoustic guitar. And at any given protest, perhaps as a scheduled part or perhaps as it wraps up, someone will burst into an unironic...