I'm equally curious about where you picked up that little nugget of misinformation. God wouldn't have put a joy button so easily within reach if he hadn't intended you to push it once in a while. Homosexual acts you do with someone of your own sex. Heterosexual acts you do with someone of the opposite sex. Masturbation is something you do with yourself.
Masturbation is done by males and females of all sexual orientations.
I am a straight female who looks forward to masturbation when my fiance is not available. He masturbates as well. We masturbate together before intercourse. It's a wonderful thing. Conventionally, straight men are supposed to get sexually aroused by the female body and vice versa.