We expect judges to make decisions based on the law, not on their personal, moral, religious, or political values. While this may be difficult, it is not impossible. We expect the same of teachers, umpires, referees, and public officials generally. To say this is not to say that these people have no values; it is to say that they must work hard to keep their values from affecting their decisions.
For example, every Major League Baseball umpire grew up with a favorite team. Do we require umpires to announce which team they liked, so that we can watch them for bias? No. Do we prevent them from umpiring games in which their childhood team participates? No. We do, however, expect them to set aside their likes and dislikes while umpiring. It's a matter of complying with the requirements of the role. If you can't do this, then you have no business occupying that role. Not everyone is cut out for every role. Wisdom consists in knowing which roles one is—and is not—cut out for.
As any reader of this blog knows, I have strong views about many things, including political philosophy. Do these views come into play in the classroom? No! I'm a professional. My job is not to indoctrinate (put a doctrine into); it is to educate. I expose my students to all significant views on each topic, from morality to religion to law to social and political philosophy. Ultimately, they decide which view, if any, to accept. Their choice, however, will be an informed one, if I am successful in my pedagogical objective.
Here is a New York Times column about journalistic impartiality. Note that impartiality is not the same as objectivity. Nobody expects reporters, umpires, or professors to get out of their skin and occupy some "view from nowhere." Nor is impartiality the same as finding a middle ground between various views or values. That's called compromise. (What would it mean for an umpire to compromise?) It is to refrain from taking sides, however tempting it may be to do so.
In my Philosophy of Religion course, for example, my job isn't to persuade my students to be theists, agnostics, or atheists (or to dissuade them from being any of these things). It is to expose them to the main arguments for and against each view. That I happen to be an atheist/agnostic is irrelevant to this task. I bend over backward to be fair to each view I discuss. Do I always succeed? Perhaps not; but that just means that, for reasons such as human weakness, ideals are not always realized. If ideals are to be rejected whenever they aren't realized, then there is no point in having ideals.
The New York Times is losing readers because its reporters are partial (i.e., not impartial). It's good to see that at least some employees of the newspaper are aware of, and concerned about, the problem.