On a spring day in Lexington, Va., fraternity row openly sports Greek letters without any apparent unease from town officials. In fact, two of these houses are across the street from the police station.   The “animal house” fraternity is around the corner.  Just how similar signs might — in some imaginary universe — represent a threat to the peace and dignity of the City of Radford is one of life’s mysteries.  Yet the city persists not only in maintaing its unconstitutional fraternity sign ban,  but also in refusing to discuss the issues.