That's just a flatly racist statement.
I watched oral arguments for this case, almost a year ago now. [Never let it be said that the wheels of justice turn quickly]. The state's lawyer was not the same dude who had represented the state at the district court, which meant that occasionally when the justices asked him what the reasoning at trial had been, he wasn't able to answer them. That said, he also gave away the farm; he conceded
that it was a race-based security decision and was trying to argue that even so
, the inmate had no case, because (a) all the state had to do was prove it was reasonable, and (b) locking down every black person whenever any black person assaulted a police officer was self-evidently reasonable. At one point, the chief judge of hte panel flat out accused him of making a racist statement; he agreed.
Given how oral arguments went, this is really not a terribly big surprise: the state has a self-evidently racist policy. It may be able to demonstrate that that racist policy is, in fact, narrowly tailored to serve a compelling state interest; but the inmates have a right to force them to prove that, and not just assert it before a compliant district court.