Ruling either way puts the US in the wrong and cal;ls into question the validity of laws which they do not want to endanger, as the form the basis of everything from the Civil Rights movement to anchor babies and would through a serious wrench in the status quo and call a lot of political agendas on both sides into question.
It's far easier to just ignore the matter entirely.
Which does not address why it was not challenged as soon and repeatedly after the Southern States were readmitted to the Union, now does it?
Yeah, they were really in a position to do jack shit while the carpetbaggers were bending them over
Are you mentally ill? By 1878 they had more power then before. They had the power to return to treating blacks like virtual slaves, denying them the vote, openly murdering them ( in South Carolina a former black US Senator with a large black following was surrounded at his home and all the people there were murdered as I recall) Grant pulled federal troops out and let the South do as it pleased after all his cronies had caused so many scandals he had no power.
I suggest you crack open a history book or two dumb ass.