Senator Grassley just grilled Kagan on Kelo, the case that suggested that states can simply grab land from A and hand it to B if B generates more tax revenue. Kagan actually said that the goal of Kelo was to "kick it back to the states" - in other words, Kagan was saying that the Court okayed the Kelo project in order to incentivize states to pass anti-Kelo laws.
Well, put me in a dress and call me Shirley if that explanation didn't just explain away the problem with Plessy v. Ferguson. That judgment said that segregation didn't violate the Fourteenth Amendment. By Kagan's logic, this was actually an attempt to incentivize states to avoid segregation laws.
This is backward thinking at its finest.