Sexual desire is dictated by the amount of testosterone and other hormones and neurotransmitters running in the body and brain. Unless your boyfriend can prove that Muslim women do not have testosterone running through their veins, his claims are void. Humans are sexual – some more so than others. Your hypocrite boyfriend needs to understand that (He is a hypocrite because he would consider his sister impure if she masturbated or had a boyfriend but there is nothing wrong with him when he masturbates or has a girlfriend. Or maybe he’s just sexist). Either way sucks anyway.
I’m a Muslim woman (girl actually – I’m 16) and I masturbate. I also wouldn’t hesitate to have a sexual relationship when I’m mature enough to have one. But then again I’ve questioned the dogma that I was preached when I was living in Saudi Arabia. There, women are not supposed to be sexual or human for that matter. If you really want to know how women are expected to behave just think about women in the Victorian Era; it’ll give you a very accurate picture of what life in the Middle-East is like for women. Oh, and don't forget the head-to-toe covering even under 125 degrees of hot sun. Your friend is right about most Muslim women not masturbating or having sexual relationships outside their marriage. But he is wrong when he tells you that that is by default or that this is how all women should be. He is being obnoxious to you and all other women when he says that masturbation on a woman’s part is “impure”.
Now to your main concern: Is he being oppressive to you. No and yes. If he is not forcing you into thinking a certain way or behaving as such, he isn’t oppressing you. But by guilt-tripping you and indirectly telling you that you need to be like his sister in order to be “pure” he is being mildly emotionally abusive. Take my word for it: Leave him. If he has the audacity to tell you what is and isn’t acceptable when it comes to YOUR sexuality (and remember this isn’t some hard-core fetish that he disapproves of; he is openly telling you that women are not supposed to be sexual at all), he is showing the signs of a control-freak. Don’t get me wrong. I’m a Muslim (well, agnostic, but I live in a non-religious but Muslim household) and I don’t approve of spreading negative stereotypes about any group of people but hard-core Muslims are scary. They are sexist and disapprove of anyone and everyone who isn’t like them. Of course it’s your choice to make at the end of the day.
Lived in Saudi Arabia for 13 years. Questioned everything I was indoctrinated to believe and chose my own liberal path.