If it was presented as "I'm black, and I'm for more equal rights in America, and he's white, so I don't think he's treating me fairly because of his heritage", which I think is more akin to how it was originally presented, they yes, people would be upset if it was proclaimed loudly and publicly in a national forum.
If it was "He's German, and I'm Jewish, therefore I don't think he's treating me fairly because of his heritage" then yes, people would be upset.
I don't know why you think it wouldn't be a big deal. There would be plenty of people denouncing statements like that. There would also be overly apologetic liberals and overly radicalized minorities defending the statements (wrongly, IMO). Those have their equivalents in the current situation as well.
Don't cast aspersions on people's character (is he violating his oath of office?) based purely on their race. We have a word for that. It's called racism, and it applies both ways.
I'm sure you're right that defendants in trials say stupid shit about judges, and I'm sure some of those comments are overtly racist. If the races in this situation were reversed, I still wouldn't vote for the hot-headed loudmouth.
Why, then, should it be shocking or appalling to hear the claim made with the parties' races reversed? Are we to assume that people who aren't white are incapable of bias? Are we to assume that a judge has no power over the people whose cases are heard in his courtroom? Is the total equality of all races a principle worth upholding, or one merely worth claiming when it's convenient, and trivial to ignore when it's not? Are we, in short, to assume that only white people can be bigots?
(And, I mean, you can argue that the question is ill-founded and wrongheaded all you like, and I realize that's the temptingly easy option. You might, though, if you're really as worried about a Trump win in November as blog posts like Mr. Altman's make out, think instead about how you might actually convince somebody who asks a question like that, instead of just trying to shout him down.)