I used to say a lot of stupid racist things. Then I got caught saying stupid racist things, and I'm afraid I argued about them, and tried to complain that I didn't mean them, but I finally realized that how people of color feel about that sort of thing is more important than how I feel about it. Now I say relatively few stupid racist things, and everybody's better off. Hollaback is moving the same process forward with street harassment. (No, it doesn't matter that you meant it as a compliment, and I'm sorry IF* you feel bad about that.)
*Not an actual apology

Thanx to Geek Feminism.