Bono did well to quell the disappointment of U2's tour cancellation by speaking his mind on Andrew Denton's Enough Rope. It's worth reading just for his answers to the problem of evil questions—a model in what might be called apologetic restraint.
Before U2 opened the Live 8 concert last year, a friend and I debated what song they'd sing. I thought 'Crumbs From Your Table', an impassioned plea to American Christians to feed the poor. It seemed obvious. But my friend thought 'Beautiful day', and she was right. It was a good corrective to my angry approach. Better to have people with you, celebrating the day and singing 'don't let it get away', rather than telling them first-up what black holes they are.
There's a time for calling for repentance, and a time for trying to throw your arms around the world.