A 23-year-old gay man was attacked on a Manhattan subway as a crowd of straphangers failed to help. Urena Morel Frankelly and his partner were on a southbound No. 2 train Monday night when a woman took a picture of them eating and her friend called them names. “Why you taking a picture?” the victim asked. “Feed you face, f-----" the suspect shouted back. Another woman with her chimed in, apparently asking the partner: “Why you with that f-----?” An argument erupted, and the two women, joined by three others plus a man, attacked Frankelly, police said. His partner tried to intervene, but the victim was repeatedly punched. The pair managed to get off the train at the next stop, West 96th St., and police were called. The victim’s left eye was swollen shut, with a cut above the socket. He was treated at St. Luke’s Hospital.