The music industry has a mixed track record when it comes to altruism: For every Concert for Bangladesh , a thoughtful and timely project that has endured as a piece of era-defining art, there is a “Do They Know It’s Christmas?,” a song conceived by a handful of rich white musicians who seemed to assume the Christian-majority Ethiopia didn’t know the most important Christian holiday. I was fearful that Together for Palestine , a huge charity event at London’s 12,500-capacity Wembley Arena