Emancipation Proclamation is actually a human rights issue. What is the the thing that all libertarians believe? It's that other people should not meddle in your life. Slavery is the most egregious violation of this short of killing you.
The Civil Rights Act was necessary at the time, but would not be necessary now. Not because there are no bigots, but because the public opinion is against them. Notice the difference: if someone doesn't hire you because their race makes them uncomfortable, it's affects you the same as any other rejection. It doesn't force you to do anything.
By the way, people still get rejected based on race all the time, it's just more hidden so it's not like the law solves the entire issue. The question of the matter is whether we should encourage the dumb racists to express that opinion on public. I would certainly want to know so that I don't accidentally patronize their establishments