Same thing can be said for western mediums too.

Steven Universe: Written by a woman, massive success despite it's network trying to kill it.
Star Vs.: Written by a woman, instant cult hit.
Harry potter: Written by women, becomes a subculture
MLP: Created by a woman, becomes an internet obsession

The vast majority of people do not care about the gender of the writer so long as the show is good and doesn't ride the diversity coat trail. Less than 10%? Try less than 1%. The /a/ trolls are not that prominent. All of 4chan would not make up 10% of all anime fans.

Sailor Moon was created by a woman and for women, and it focuses on the girls' characters and feelings much more than it does their bodies. If anime had a misoginy problem, this anime would be infamous and hated instead of a popular classic and loved. At most, I am willing to believe that the worst spawns from /a/ are misogynistic pricks who happen to like anime, and that is, like, less than 10% of anime fans, and we all know they pirate everything they watch instead of subbing to CrunchyRoll.