I think it's not only a yaoi thing. Me thinks they are going to or have went to move to yuri soon but they came to yaoi cos it's the largest fandom here and where love=rape is well known for. 6000 plus yaoi compared to 700 plus yuri is also a reason. For yuri there would be different issues as well.
Yet they leave others. alone.It is only Japan they go after. the Jpn. senate had to issue a statement to protect their gaming industry after they went after them. Making claims it was sexiest, ect. Some one tried to get the UN to ban the sale of their games world wide. (Yes, they strive to own and dominate with thought.) It failed bec. some one from the U.S said no.
Take a highly regarded yuri title. Like, Kannazuki no Miko.
There's a girl that rapes another girl. But it's portrayed as an act of love and is forgiven because it's *so pure*. It's implied that rape isn't really rape when it's girls on girls, as it's done out of love.
The problem we see here is that it's not related to any genre, but probably the Japanese culture (or well, human nature, whatever it is). Anime involves regularly sexual or domestic abuse; when it comes to anime porn even more so. Gays, lesbians, straights (especially them, obviously), everyone has their share of it.
So let's stop lashing specifically on yaoi fans for such a thing u_u