Homosexuality = Sodomy

Apart from the Gender implications of the concept of 'homosexuality' (of painting man to man sexual interest as feminine in itself), the concept of 'homosexuality' also serves to discourage man to man desire in another way -- it has the same implications as calling a man who has sex with another male as being a sodomite (which doesn't have any third gender implications), but holds its stigma because of religious and social injunctions against the act of 'sodomy'.

A significant number of men, especially straight males, like other men sexually but are more interested in the bodies of the other men, rather than in performing 'sodomy' with them.