I suspect they are making as simple an argument as possible. Pre-emption. The more complicated they make the claims, the more opportunity for a defense lawyer to poke holes in it with the Constitution and the harder for any Judge to rule in favor.
Specifically on the discrimination angle, any argument about profiling or discrimination would open the door to the defense to argue illegals do not have the civil rights afforded US Citizens.
That’s what I was getting at. You just said it far better. Thanks.