Ann Althouse has the best take on this:

As some commenters are pointing out, the phrase “so-called judge” could be called an attack on the man. But the only basis for saying “so-called judge” is what the man in the robe is doing in this particular case. There’s nothing against him as an individual. It’s very close to saying, in a substantive legal way, that this is a man who is acting beyond his proper judicial power. This parallels what the judge is saying: Trump is doing things under the appearance of being President, but what he is doing is beyond the powers of the President. This is just a man, not someone who can wield governmental power. That’s not a personal attack. That’s the rule of law.