They are common carriers. The elephant in the room is the Visa/Mastercard duopoly.

While I agree with your point, I think banning redheads would violate Title II of the Civil Rights Act of 1964.

No; hair color is not what that legislation covers.

It is entirely legal in the United States to discriminate against redheads, or people whose names start with B, or Hacker News users, or people who enjoy skiing.

I do believe that there could be an argument that discrimination on hair color could fall under national origin or color:

Under 29 CFR § 1606.1, national origin is defined as but not limited to: An individual's, or his or her ancestor's, place of origin; or because an individual has the physical, cultural or linguistic characteristics of a national origin group.

With the current court, almost certainly not; they're not inclined to expand the definition of "disparate impact" like that.

If a future Court ever decides hair color denotes national origin, fall back to a different example of your choosing; people with tattoos, Mac users, viola players.

Hair color is something you're born with and is a genetic mutation based off lineage and other factors. I don't think they directly corelate and it wouldn't necessarily even make it to the Supreme Court. Most businesses aren't going to appeal to say that they can discriminate based on hair color nor willingly admit to doing so, nor would they ever likely make the argument that they did it and that it is okay.

The law doesn’t say “things you are born with”, though. That’s a common theme with the specific categories it does name, but only those specific categories are protected.

It isn't specifically limited to those specific narrow words by the most limited means you're thinking. I'm sure they could make that argument, but only a fool would risk a discrimination lawsuit based on hair color. Even if that is the specific reason a person would have to be either a fool or want to try to challenge the law, and there is no guarantee after losing that the Supreme Court would even take the case. I don't think the Supreme Court would even want to touch such a case nor that it would be ruled on in the manner you're thinking.

You could discriminate against people with dyed hair colors, but I find it hard to believe that any court would say that a person's natural hair is not a physical characteristic of a national origin group.

https://www.fwlaw.com/insights/is-hair-a-protected-class#:~:....

If you read that closely, it doesn't apply in the slightest to the example.

As a red head, this made me chuckle. Thank you.