When my son, who’s 19, called from Minneapolis on Saturday night, I was watching the livestream of protesters defying curfew there for the second night in a row, and listening to young people dry heave, like my students in Colombia, from the tear gas. Because he has first-aid training for mountaineering, my son was volunteering in a medical tent clearly identified with a red cross, but the state police fired on them with tear-gas canisters and rubber bullets, and he and his friends hoofed it home. The real medics told him to stay in for the night. It was going to get rough.