ROBERT A. STRONG Guest Columnist LEXINGTON Republican critics of President Barack Obama’s low-key response to the unfolding events in Iran are fond of saying that this president should be more like Ronald Reagan who, when the Cold War was winding down, railed against “the evil empire” and boldly told Mr. Gorbachev to tear down the wall that separated East and West Berlin. There is no question that President Reagan was a rhetorical cold warrior of the highest order, but he was not actually our chief executive when the political revolutions in Eastern Europe and the Soviet Union came to full fruition.