Men usually only notice blatant sexism. This is because they have the privilege of not noticing. But women who do notice subtle forms of discrimination need to talk about them. Especially with other women who may be facing the same kinds of misogyny and incorrectly interpreting sexist interactions as being simply personal or the woman's own fault.
I've been dealing with a professor who has a particularly crafty way of marginalizing female students. He talks about how much he hates sexism, and he even scolded me for liking a film that he felt was sexist. See? He's even more sensitive than the radical feminist in the class! But all along, he's also been telling me (in person and by e-mail) that I need to be less theoretical and less intellectual and that I should stop viewing the world from my specific experiential viewpoint (ie that of living as a woman). Even my privilege-blinded male colleagues got a good laugh out of that one. Yessir! I will immediately stop being "a woman" and will be "a person" like you! Hahahahaha. Good one.
The problem with this kind of thing is that it is usually subtle enough that an individual woman will tend to doubt that she really saw or heard something that devalued her. I even doubted myself when my argument that the 1950s were an era marked by visible patriarchy garnered the following reply: "If I do have one criticism with the way you approach the world, it is that you have developed a very highly tuned and critical eye that tends to see things through very specific theoretical [read: feminism] (and, of course, experiential) vantage points. These inform everything you do, but they are only one of many possible ways to view the world - and are no more right then other models." So feminism is no more right than other models of viewing the world! All the alternative viewpoints are equally valid. Note that this professor describes himself as a "deep relativist." Great, I feel so safe in your class, dude.
I think this professor really is well-intentioned, but he doesn't understand that it is incredibly offensive to tell a young, intellectual woman that she should stop being so damn smart about things. And because I assumed he was well-intentioned in his e-mail, I tried very hard to rationalize his words. But finally one of my female professors explained that, no, I wasn't a "crazy, hysterical woman," that he was indeed treating me differently from how he treats intellectual male students, and that he has a habit of using other subtle-or-not-so-subtle sexist language in dealing with his female colleagues among the faculty.
It really made my day to have my feelings of frustration heard and confirmed. Because women are socialized to not notice sexism or to ignore it, we need to point it out when it occurs. Less for the benefit of the man (or woman) who is perpetuating misogyny but rather for the onlookers and the quiet women who are struggling with how to name the oppression they feel. It was a similar feeling (though in smaller scale) to how I felt when Comrade Dziga confirmed that my "creeper" alarms about a stalker were justified. Women are so thoroughly schooled to doubt ourselves and give men the benefit of the doubt. It is astonishing.
Much of this post (especially this latter part) was inspired by an article I recently re-discovered. I came across the article that I referenced in my earlier post about men who don't respect women's boundaries. This article is fantastic; it says everything I was trying to say so much better than I could. Thank you, Starling, of Shapely Prose, for "Schrodinger's Rapist."