A judge has the right to rule. One of the factors in that ruling is how the defendant acts. If you show contriteness, and accept responsibility they will be more lenient. If they don't they will judged more harshly. That isn't showing partiality. It's a standard that applies to anyone. The judgement reflects that.If the judge ruled more harshly because of simple rhetoric then I would hardly say he’s impartial.
You can't even claim he was judged as harshly as the prosecution demanded. They asked for disolvement of the company and a lifetime ban for Trump for dealing in New York. The judge didn't rule that.