Of course, Orange is the New Black is under no obligation to accurately represent prison demographics, and just because they're a minority in prison doesn't mean that women's stories there aren't important. The problem is that the ways in which OITNB focuses on women rather than men seem to be linked to stereotypically gendered ideas about who can be a victim and who can't.
The few male prisoners who are shown on OITNB are presented in almost aggressively stereotypical ways. Early in the second season, when Piper (Taylor Schilling) is being moved to Chicago to testify in a drug trial, we're shown a number of male inmates being transported as well. They are presented as a threatening, uniform mass. The one prisoner who is given a more substantial role is a black man who makes frightening sexual verbal advances towards Piper; he's a contract killer and refers to himself, apparently without irony, as a "super-predator." He eventually delivers a message for Piper in exchange for her dirty panties. The one male prisoner we meet, then, is violent and abusive, with a sexual kink that is presented as laughable and repulsive. He deviant, dangerous, and the show seems to think that he is exactly where he belong—behind bars.
Female prisoners on the show are treated very differently. They may be violent and may be queer, but they are, for the most part, presented as sympathetic. This seems like a feminist move, on the surface. But the inability to extend that sympathy to male inmates, raises a disturbing possibility: that the show is condescending to women while reinforcing old and destructive attitudes about men.
Adam Jones argues in his book Gender Inclusive that empathy for victims is often, in our culture, dependent on the victim being a woman. As he says, "We live in a culture that is trained to view the violent victimization of women as a much more serious offense than the violent victimization of men."
Jones includes a wide range of supportive evidence. Male victims of domestic violence are almost entirely ignored, though domestic violence is perpetrated by men and women at about equal rates (though, Jones points out, violence by men is disproportionately more serious because of strength and weight difference.) In Bosnia, human-rights organizations focused on the (horrible, important) suffering of women rape victims and refugees, while largely ignoring the mass, gender-targeted killing of "battle-age" men. Similarly, violent attacks on women receive much more media attention than violent attacks on men, though men are substantially more likely to be attacked.
In other words, male victimization is seen as natural, or not worth commenting on. As a result, Jones argues, it is difficult to see that, "the most severe and institutionalized human rights abuses in the United States are overwhelmingly inflicted upon men, especially—though far from exclusively—younger, poorer, and minority men."