Age/Sex Flip-flop?

My mind is completely blown today. I shown Black Butler for the teen anime club at the library I volunteer at. With past titles as Gravitation and Ouran Host Club, it is rather obvious the crowd consists for mainly girls. Teenaged fangirls. They are good kids, until one topic sets them off; Yaoi. Any kind, any coupling, any series, they are full of imagination and are open to say so. *Sigh* The things I go through to see the smile of a cute librarian in glasses.

While looking through emails, it hit me. The teen anime clubs I know of are also mainly girls. However, the older clubs that I have seen, SDAnimanga and UCSD, are mainly guys. Now, is age the factor? At what point do the roles change and the fanboys out number fangirls? A great mystery, or wasted thoughts of a man surrounded by teenaged girls fanaticizing about two guys naked, or worse.  I am so tired.