I don't think Laurents ever said that Tony and Riff were gay. He just suggested that they may have engaged in some adolescent sexual horseplay when they were sharing a bedroom. Two gang members are like two guys on a high school football team or two army buddies. It has nothing to do with one's sexuality. It's the situation, the closeness, the stress, the camaraderie, the tension, winning a key game, surviving a battle in war, stuff like that. Think of films like Ben-Hur, Platoon, North Dallas Forty, Jarhead, Jim Bouton's autobiographical Ball Four: The Final Pitch. Just saying.