GARDEN CITY - Prosecutors say a man arrested for touching himself inappropriately at Hofstra University yesterday had already been banned from campus for a similar incident. Karl Wildermuth, 70, allegedly began masturbating while sitting behind a female student in the campus library. Prosecutors say he was thrown off the campus back in 2000 for another incident involving lewdness. According to prosecutors, the woman who caught Wildermuth in the act yesterday recognized him as the same man who grabbed her buttocks three years ago in the same library. That time, he got away before police arrived, officials say. Wildermuth, who lives in an assisted living facility, has been charged with forcible touching and public lewdness.