A few years ago I was at that good used bookstore on 20th Street by the Free Library and saw a crowd gathering on the Parkway: Bruce Springsteen was about to play a short concert to promote Obama’s first run for president. His seven-song acoustic set was excellent, just him and an acoustic guitar and songs of struggle and hope, but what sticks with me is his mid-set speech, which began with a cogent artistic statement: more…