Yes, and Trump should be pointing out his specific conflicts of interest (there are many), and not his heritage.
The judge's problem may indeed be linked to his heritage, but Trump is setting himself up for an attack by making that claim without a specific admission from the judge.
I don’t understand why his lawyers haven’t yet filed a motion to request the judge to recuse himself. In that way, Trump can lay out all the details showing that the Mexican judge cannot properly handle Trump’s case.