What he's doing is natural and exciting!

John found that he enjoyed the idea of the girls watching him, but the look of disgust wasn't pleasant. He quickly wished that masturbation should be as natural as nudity now was, but that no other man ever felt like doing it in his presence (and would feel uncomfortable enough to leave). Women, on the other hand, were less inhibited, and had no problem masturbating in front of each other or him. Also, the sight of an erect dick would always make women feel sexy. In fact, the sight of a man stroking himself was arousing, but a man looking at them while he did so made the need to touch themselves overpowering. Finally he added that seeing, feeling or just knowing that a man was ejaculating would cause any woman to reach orgasm at the same time.

He watched the men shuffle out of the bathroom, then he looked at the two girls whom he had seen before. The one who had look curious now had her hand to her mound and was slowly rubbing herself, while the formerly disgusted one was unsuccessfully trying not to look. John looked directly at her and turned his erection toward her. She saw this, groaned with lust, and her hand went straight between her legs and she began rubbing herself furiously.

John looked around the room. All the women were looking at him intently and many were jilling themselves. John made sure to look at all those who were 'holding out' to get the started, and then enjoyed the effect he was having.