On a hot day last week, the pavements outside Columbia University were heaving. About 200 protesters were gathered, making a noise that was bigger than their numbers, raising pro-Palestine chants and signs. It was a disparate crowd, diverse across ethnicities and generations. “I’ve lived in this neighbourhood all my life,” said one of them when I asked him why he was there. One smiling elderly lady walked through the crowd offering small bottles of water. A helicopter circled overhead. The police who encircled the crowd were jittery, yelling at passersby to keep moving, and raising the temperature of what was...