I agree with what you're saying with regards to rape, but the idea of the myth of innocence applies to almost any crime. The idea is that, for example, if two men are standing there, a police officer walks by and one says "hey, that guy just hit me and took my mp3 player!" the officer will look into it, but regard neither party as more truthful, while a woman accusing a guy of that same crime would be immediately believed because of her gender. Or, one that I've seen happen personally: A guy I know, when he goes to the bar, puts his money on the bar in front of him with his car keys and stays there until he leaves for the night. I was sitting on his left, a young woman was on his right. The bar was packed. The young woman ordered a drink, the bartender brought the drink but took one of my friends 10's to pay for it. When he came back with the change and put it in front of the girl my friend told the bartender what happened, who looked at the young woman and said "Wasn't that your ten?" she said "yeah". My friend got angry, and we got kicked out of the bar. The bartender (to my knowledge) had no reason to assume my friend was lying, but believed what she said, in my opinion because she was a young woman and my friend wasn't. Maybe the two knew each other and scammed people like that often, I don't know.
when it comes to sexual assault, masculinists want to see cases of sexual assault reported by men taken equally as seriously as women. If a man reports having gotten drunk and sexually assaulted most people would laugh, or even believe that men cannot be assulted sexually by women. Men being sexually assaulted, especially in prison, is a common joke. We would like the legal system to acknowledge that sexual assault against men is real, and not funny, and should be taken seriously.