First. Killing people and burning shit down is illegal. Do not need different laws to prevent it.
Ah Libertarianism. Saying only the laws in the Constitution matter, and that all other laws don't matter, instead of just using logic in general when it comes to good and bad laws. Well, unfair treatment of non-white humans was made illegal in the Constitution, fyi. Also, your utopian Libertarian view of "XYZ would be awesome if there were no laws governing XYZ thing" when it comes to this segregation is horribly flawed. What this would mean in America is *segregation*, where you'd end up with a lot of racist cities and states once again, and life would be even more rough than it is for non-white humans.
Clearly bad and harmful things should be illegal. Things that aren't shouldn't be. Most Americans agree with that! But segregation not being illegal? Most Americans would disagree. Yes yes, you want those dirty (group of individuals who have done nothing wrong) out of your store, but, well, they've done nothing wrong, so fuck you.