“Ride the D,” the LA Metro said, cheekily. But not even the X-rated slogan (or the racy merch that came with it) has enticed Angelenos to ride the newest extension of the light rail system. The California Post visited the new D Line extension last Thursday, on rush hour — and the date of the opening of the World Cup. We found it virtually empty. There were Metro staff, and some homeless people — and that was it, in the gleaming, newly-opened stations. Public transportation has a role to play in