You're saying you need a good reason to ban people, then you have to legislate exactly what a good reason is, because you've now legislated what a bad reason is (black/gay/etc.).

Do you think that, because of the existence of legislation regulating speed limits, that there must also be legislation that says literally everything that you are allowed to do?

And if they both happen to be the only black people in your business, then you're opening yourself up to being sued for discriminating based on race.

I guess? Based solely on the tiny fact pattern I gave, it's a pretty easy inference that they aren't being discriminated against, because they are being violent and there is no comparative behavior to see if it is discriminatory. I don't think any court or jury would find in their favor, but sure, I guess a claim could exist there.

And if the black person threatened violence when the white person didn't? Still can't kick just the black person out?

No, you can definitely do that. See, because then there is behavior that is warranting the refusal, so it isn't based on their being a protected class. It is not a super difficult concept. If the reason they are being refused service is because they are a member of a protected class, then that is discriminatory and the business can't do that.

And who decides what is innate? Are you allowed to ban someone that are super loud, obnoxious and rude to your staff? That's an innate quality to a lot of people.

The general public decides what is innate. Judges are elected (or appointed by elected officials), and they interpret laws and decide if things are unconstitutional and whatnot. Juries are the "voice of the common folk," so if there is a case where someone is being loud, obnoxious, and rude to a business owner and a jury thinks that should be protected behavior, they'll make that decision. Legislators are elected, and they make laws for all of us that define all kinds of things.

Again, not a difficult or super complex concept. What you're arguing has been argued and litigated a thousand times over, and your ideas have been decided against time and time again by people that are smarter and more adept at this than either of us. You obviously don't understand the concepts here and think that you're coming up with novel thoughts about this topic. Do you really think that the judges that make these decisions never thought about "well gee, what if they intentionally make the cakes bad for the gays? Guess we'll never be able to afford civil rights to minorities now!" You're coming up with the most basic, simple ideas people have ever had on this topic, and acting like it's some kind of gotcha