I think the issue is rape by known persons is seen by many people as acceptable, or at least not as egregious a crime as rape by a stranger.
Rape by a stranger is more directly cut and dry, I would suppose. More likely for there to have been a violent struggle, which generates evidence, which fits the naive model of "it looks like a crime." Its also probably very likely to get reported to the police as people don't appreciate strangers coming in and doing bad things.
I used to know a woman who claimed she was raped, and when discussed it was more of a case of a very pushy boyfriend. I asked why she didn't report it and I was told that she "didn't want him to get in to trouble" [e.g. the whole mess of sex offense registry, prison, effectively being permanently unemployable] and it became unclear whether it was actually forced or not, but when pointed in the direction of the police she didn't consider it worth filing. I thought it was incredibly strange behavior, but sometimes the woman might actually have been directly abused and for whatever reason chooses not to file it, and other times a different woman is simply filing rape charges because she knows our culture will automatically ruin his career and reputation even if the case is dropped a week later.
Would we have this same idea of taking responsibility for drunkeness if straight men were often being raped by people they thought they knew?
I doubt it. There's an eerily high number of pseudo-equality people who think its impossible to be racist against white folk, and even those who deem it "reverse racism", even though its just plain racism. Similarly, a lot of misguided feminists who seem to think being a man is sunshine and rainbows where nothing is ever your fault and you just get handed briefcases of privilege money all day.