Block, as you might have guessed, is the subject of some amount of controversy. We should point out right up front that he uses a strict libertarian (rather than a strict white supremacist) justification for his views. So he doesn't, for example, oppose all civil rights laws because he hates black people; he opposes civil rights laws because he believes they infringe upon the freedom of business owners to decide who they want to serve.
Strict libertarianism may not be a good ethical position, but is at least a semi-coherent defensible set of beliefs. Unfortunately for Walter Block, he combines his libertarianism with casual racism. That does not help his cause. In a comprehensive rundown of Block's controversies today, Inside Higher Ed quotes from an article Block wrote last year entitled "Chris Selley is a Pussy Libertarian; I'm Not." Bolding ours:
"Free association is a very important aspect of liberty. It is crucial. Indeed, its lack was the major problem with slavery. The slaves could not quit. They were forced to 'associate' with their masters when they would have vastly preferred not to do so," Block writes.
What follows, however, is unlikely to win over many of his critics. Block adds in the essay: "Otherwise, slavery wasn't so bad. You could pick cotton, sing songs, be fed nice gruel, etc. The only real problem was that this relationship was compulsory."
Often, Libertarians would benefit from exercising their freedom to shut the fuck up.