Libertarians/anarchists do not necessarily oppose racism, sexism, etc. Opposition to such prejudices is not part of the definition of libertarianism or anarchism, and it is certainly possible for people who are prejudiced against blacks or Jews, for example, to be anarchists or libertarians.
It's the initiation of force that anarchists and libertarians morally condemn -- not personal prejudices. I happen to be prejudiced against people who work for government. I don't run around burning their houses or otherwise doing them harm, but I generally regard any misfortunes they suffer as well-deserved. So you gonna drum me out of the anarchist club?
See, just about everybody has some prejudices, as a result of our individual upbringing, education, values and experiences. In an anarchist society where the initiation of force is regarded as evil, the social effects of prejudice are minimized. In statist societies where people can vote to institutionalize and legalize their prejudices, the effects of prejudice are multiplied.
To claim that being a libertarian or anarchist means opposing prejudice is entirely wrong. Being free means you are free to have whatever prejudices you damn well please -- you're just not free to initiate force against the folks you hate. (Actually you're free to do ANYTHING -- but you'll face serious consequences and costs, if you do.)
Recommended reading: The Most Dangerous Superstition, http://www.amazon.com/Most-Dangerous-Superstition-Larken-Ros...
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