I agree with this statement as well. I would suggest though, that it's being strawman'ed. Let's "steelman" the argument just as we try to do here on HN. For example, this statement is a strawman: "Trump said that a judge is inherently biased just because his parents are Mexican." The steelman would be something like, "Trump claimed that a judge had a conflict of interest against him. The judge was born in America, but has Mexican parents, which Trump believes could cause him to have a bias due to Trump's anti-Mexican policy proposals, such as the border wall."

Should he be calling the judge's ability to do his job into question? I don't think so, no. But let's argue against what he actually said - in fact, go even further than that and interpret it in the most reasonable way possible - because it's more likely to result in useful discussion among people of differing opinions.