While discussing sexism with my wife, there have been a number of times where I've said "I just don't see it" — meaning either that I literally have never seen the behavior in question, or that I didn't see the interpretation being given. To the first meaning there is a clear rebuttal: its easy to miss something that doesn't affect you (that is, affect me, the guy in the room). With respect to the second, one aspect is that I both don't give enough credit to most people to be deliberately coming up with many of the examples of sexism I've heard about, and I generally assume innocence of motive.

Well, Shakesville's Feminism 101: "Sexism is a matter of opinion" does an excellent job in pointing out the flaws in this naïve analysis, including the use of an excellent Matrix-metaphor. The whole thing is worth reading, but one particular paragraph stuck with me, partially because it applies equally well with the issue of racism:

Let me quickly stipulate and clarify that one can unintentionally express sexism. That innocent intent, or ignorance of the history of how women have been marginalized, does not, however, in any way change the quality of what was being expressed. Something can still be expressed sexism even if the speaker's intent was not to oppress women. And particularly if it does fit neatly into a historical pattern, it necessarily conjures that pattern of sexism, intentionally or not.