'Masculinity' is defined very broadly. For instance, a sociologist spend 18 months going to a California high school and observing the ways in which boys called each other fags - what things made you a fag, essentially:
"I saw and heard boys imitate presumed faggots and hurl the fag epithet so frequently at one another that I came to call it a "fag discourse." I use the term fag and not gay, advisedly. Boys at River High repeatedly differentiated fags from gay men. For these boys gay men could still be masculine, whereas a fag could never be masculine. Thus the term "gay" functioned as a generic insult meaning "stupid" or "lame" whereas "fag" invoked a very specific gendered slur, directed at other boys. For these boys a fag was a failed, feminine man who, in all likelihood, was also gay. Boys participated in a fag discourse to ensure that others saw them as masculine by renouncing any fag-like behavior or same-sex desire. They did this by imitating fags and calling other boys fags. Boys imitated fags by lisping, mincing and pretending to sexually desire men, drawing laughs from male audiences who howled at these imitations.
They frantically lobbed the fag epithet at one another, in a sort of compulsive name calling ritual. In the context of River High (the pseudonym of the school where I conducted this research) being called a fag had as much to do with failing at tasks of masculinity as it did with sexual desire. More often than not these fag-like behaviors were those associated with femininity. Exhibiting stupidity, emotions, or incompetence, caring too much about clothing, touching another guy, or dancing were all things which could render a boy vulnerable to the fag epithet. In this sense what I call a fag discourse is not just about homophobia, it is about a particularly gendered homophobia as these renouncements of the fag are as much about repudiating femininity as they are about denying same-sex desire."
http://www.insidehighered.com/views/2007/06/28/pascoe