"One of the things I learned in my Gender Studies minor in college is that just because something seems sexist to others doens't mean that's the intent."

Basic principle in oppression theory (any form of oppression): just because the intent isn't malicious doesn't mean the act itself is automatically not sexist (or racist or whatever ist). Good intentions have driven systems of oppression for centuries. The intention behind an act doesn't immediately decide whether or not the act itself is sexist (or racist or whatever).

And I gotta second the derailingfordummies link.