by BYRON YORKA brief moment Feb. 13 showed why President Obama can't win when it comes to the Keystone XL pipeline. In front of the White House, protesters led by actress Daryl Hannah and the head of the Sierra Club demanded Obama kill the project. Just a few blocks away, the head of the AFL-CIO's powerful Building and Construction Trades Department joined with the American Petroleum Institute to demand Obama approve it.Obama's friends in the environmental movement and Hollywood on one side.