First, just to clear the air...
Stop referencing the USA Deep South as a hotbed of discrimination. We have no monopoly on that activity. For instance, Ferguson, with all the shooting incidents, is not part of the original USA Deep South. I see things on the news in which European countries are clashing with Islamic immigrants over things like wearing hajibs in a school. Detroit had riots a few years ago. Wyoming was where gay-bashing went to the limit with Matthew Shepard. Shall we discuss the atrocities of the Darfur region or the incredible slaughters of the Hutus vs. Tutsis and the "ethnic cleansing" of Kosovo some years ago? What about the class discrimination in India regarding the "untouchable" class and other groups?
No nation, no group, and no continent has a monopoly on discrimination. It is deeply ingrained within human nature, stemming from our reptilian ancestry that was incredibly territorial. We have always had problems or conflicts involving the "ascendancy of me and mine over thee and thine." Grouping by race, by gender, by gender preference, by religion, ... just excuses.
So the question becomes "why can't I sell my xxxx to whomever I want?" To me, the differentiator is whether my act of selling involves a limited-scope transaction (such as, say, a garage sale) vs. selling houses to people in a subdivision. Let me explain a bit more to expose the point I think is important.
The garage sale is very likely to be privately managed based on the sale of privately owned material with limited advertising. I think it would be incredibly unkind but not illegal to refuse to sell something to someone who triggered that discriminatory response within you.
Selling houses, unless you require the buyers to pay cash up-front without going through a loan company, brings into play that you are getting the money for that sale through a public lender whose assets are insured by the government and who, because of interstate banking laws, might be required to scrupulously avoid discrimination. The housing seller is taking advantage of a public but often not obvious government benefit.
My understanding is that it has always been legal to request unruly customers / clients to leave your place of business because you have a responsibility to your "ruly" customers and clients to protect them while they are in your establishment. When I was a younger man playing music in smokey, smelly, dark Bourbon Street bars, we still knew to call the bouncer when someone became a danger to others. As unlikely as it might seem, even the businesses that cater to morally questionable activities still have their standards. We didn't eject gays or blacks or women. We got rid of brawlers.
The question remains, what is freedom in the context of this discussion? Given the violent and isolationist proclivities of mankind, freedom is a chimera - an impossible creature. We can only hope to minimize the damage that we do to one another by being the animals that we are, barely covered by the veneer of civilization.
The question came up about why we have to have laws about this? The answer is that people have a massive social inertia. They abhor change, so sometimes the only way to change them is to force them as a matter of law - because they WON'T change as a matter of social pressure. They will merely withdraw into their own little clique and play "turtle" if you confront them.
Is there a solution? I doubt that we have matured enough as a species for a true solution to be found yet. The laws are not curative - they are palliative. What is freedom? It is the ability to live in a place where we don't need quite as many laws to patch up our wounded society. We seek that others might find enlightenment to recognize the inherent humanity in all of us. The sad part is that others don't always run to the light. Sometimes they skulk around in the dark. And that is why I doubt that it will get better fast.
Now, a more direct - if somewhat cynical answer - to "why do we have so many laws?" is that the people we send to Congress have to do SOMETHING to prove they deserve to be paid... even if their efforts ARE wasted on something that can't be fixed by laws.