Thousand times this.
I know that things like racism and sexism is bad and evil. But I also know that I am these things — subconsciously. Having lived in a country with a long tradition of racism and sexism, and given I've ever talked to a black person for a first time half a year ago, I know that there's no chance that I don't have these stereotypes inside on some level. Of course, I try to fight that and become a better person, and on a rational level I know exactly why these traits are evil.
But when I'm trying to explain it to someone, too often they just hear "I'm racist" or "I'm sexist" and decide that I'm a total asshole :(