But it's also pretty clear that the doctrine of disparate impact, which is what he asked about, has been clarified and nuanced through litigation of those statutes.

Yes, of course, though it has nothing to do with legal basis -- it's interpretation of the law which is what the court system does all the time.

over many decades, the courts have not overturned this doctrine due to any philosophical objections of litigants.

Courts do not do that. A philosophical objection is not a legal objection -- a court can overturn a law only by deciding that it is unconstitutional.

But I am unsure what is the point that you are making. Is it that both politically and legally the Civil Rights Act is untouchable in the US? Sure, but that's pretty obvious...