WASHINGTON (AP) -- Sen. John McCain threatened on Tuesday to cut short a speech to union leaders who booed his immigration views and later challenged his statements on organized labor and the Iraq war. "If you like, I will leave," McCain told the AFL-CIO's Building and Construction Trades Department, pivoting briefly from the lectern. He returned to the microphone after the crowd quieted. "OK, then please give me the courtesy I would give you." It was a contentious session that tested McCain's commitment to the straight-talking image he honed during his failed 2000 presidential bid. An underdog six years ago,...