I fully support gender equality and I think it's important to discuss problems like domestic abuse -- even within specific cultures as case studies (like Japan) -- but there's a difference between culture and race, which if misunderstood is outright racism. Take lolicon manga: lots of people really think that Japan must be full of pedophiles since there's lolicon manga everywhere. That's like saying a person is a pedophile simply being he's Japanese. Similarly with r***, it's a two-sided coin: you can argue for better protection of women and women's rights in Japan (and rightly so), but by focusing exclusively on r*** in Japan (or by ignoring r*** in other cultures), you easily give the wrong impression that Japanese men are rapists, as if their race is a determining factor.
Simply put, it's not the race that causes a man r*** someone. It's a psychological issue that comes from that person's environment, and frankly, it's not as if Japan is the only nation with problems of domestic abuse (unreported r*** occurs everywhere). One man is no more likely to r*** a woman because he's Japanese than another man because he's Caucasian.
Really, you could replace Japan/Japanese with America/American (or any other country/ethnicity) in just about all of the comments in this thread and they will still be true. Except maybe for manga, as in OP's question. And to that, I submit that manga is an incredibly liberal medium of artistic expression on which all sorts of taboo subjects are "discussed", and that the West simply doesn't have a similar medium (all of our "r***" content is either hyper-real as with "gangbang" porn, or surreal/abstract as with books/novels). Western comics/cartoons are so engrained with the "just for children" stigma, and just the thought of injecting sex or violence into them sends parents into a panic (as if adult manga is meant to be read by children). Besides, the average reader of adult manga is about as likely to r*** someone as an average American who watches porn.