"SUTTON." By J.R. Moehringer. Hyperion. $27.99.Willie Sutton was a thug with a fan club. He robbed banks at gunpoint. If a manager refused to open the safe, he would threaten to kill the tellers.But, as J.R. Moehringer points out in "Sutton," his fictionalized excursion through the criminal's career from the 1930s through the 1950s, Willie was a "god in parts of Brooklyn." Why? Because he had the sympathies of a public for whom the local lender was more Old Man Potter than George Bailey.