Sen. Lindsey Graham warned President Donald Trump Friday that pulling troops out of Afghanistan could lay the groundwork for another 9/11.Trump is traveling to Camp David on Friday with his chief national security aides to discuss the path forward for the 16-year-old U.S. war there.The South Carolina Republican urged Trump in a statement to “listen to his generals” — an apparent request for the president to prioritize the views of military commanders over those of his just-dismissed chief strategist Steve Bannon, who reportedly wants to replace U.S.