MADONNA’S world tour began in typically provocative fashion when the pop singer hung from a cross, shouted an obscenity at an image of President Bush, showed video footage that seemed to compare Tony Blair to Adolf Hitler, and writhed around on a device that combined a horse’s saddle with a stripper’s pole.As if that were not enough, the singer also wore a crown of thorns, dressed up as various male icons — James Brown and John Travolta included — and even briefly played the electric guitar. Early reviews of the event on Sunday night were positive, but the show failed...