According to wingnut “pastor” Mark Driscoll, that is:
First, masturbation can be a form of homosexuality because it is a sexual act that does not involve a woman. If a man were to masturbate while engaged in other forms of sexual intimacy with his wife then he would not be doing so in a homosexual way. However, any man who does so without his wife in the room is bordering on homosexual activity, particularly if he’s watching himself in a mirror and being turned on by his own male body.
So there you have it: anytime a male — even a heterosexual one — masturbates alone, he risks engaging in homosexuality.