I'm the furthest thing from a Trump supporter, but it is a significant leap to take his believe that a judge with Mexican heritage would be biased against him due to his anti-Mexican agenda, and turn that into an opposition of all people of Mexican descent. Trump has said some despicable things, but saying that a person of Mexican descent might be biased against him because he's basically a dick to Mexico seems reasonably logical. Now, claiming that that's grounds for the judge to recuse himself is quite a stretch, but I don't personally see it as racist. I also think that stretching to label questionable things as racist is counter-productive; it dilutes the meaning, and makes it more difficult to call out the extreme, blatant racism that's going elsewhere.