An article published February 26, 2013 in the New York Times, discusses the case of Judge Vince A Sicari. Judge Sicari works as a judge in the court system in South Hackensack, NJ. But he also works as a stand up comic, warming up crowds at The Daily Show and performing routines at Caroline's on Broadway. And critically, he works as an actor on the show "What Would you Do?" On this show in particular, he often plays characters that are bigoted, mysogonistic, or otherwise unfriendly, in order to get a reaction from unsuspecting passers by (in a sort of candid-camera way). He is also considered an "edgy" comic in his stand up routines. A judicial committee has recently decided that Judge Sicari should not be allowed to play these characters and be a judge at the same time.
The arguement against this ruling, being made by Judge Sicari, is that his ability to work in court and his ability to work a crowd are two different things, being done by two different people. One is not connected to the other. The arguement made by his opposition is that if someone saw him make a homophobic comment in character and then had to face him as a judge, they may be uncomfortable, or question his impartiality.
The real question is: is the judge behaving in ways that reflect his real personality? If not, do the things he says echo how he feels in real life and how he may approach his judicial work? Could he possibly change his opinions and ways of thinking as a result of playing these characters, or, more importantly, are these characters a reflection of what he's actually thinking?
There is some research to bear on these questions, although no research has looked at them directly, and the results tend to be conflicting. We know that individuals who are asked to write an essay or give a speech about a topic they don't agree with don't necessarily change their attitudes or beliefs, but sometimes there is movement. However, we also know that when an individual fakes an emotion, they can change their emotional state, although we don't know for how long, or if this change affects behavior. And of course in neither case are the participants in these studies acting. The difference may lie between emotional processes (which may be more changable via acting) versus cognitive processes (which may be less changable).
A lot also depends on whether the judge in question is creating and writing the characters himself. Playing a part someone else wrote is different than coming up with a comedy routine that you wrote yourself. One (the comedy routine) is necessarily reflective of your way of thinking. Even if it's a character you came up with yourself--you are in charge of what that character says. But playing a character in a script is trickier, and I think there are layers that aren't being taken into account, steming from a lack of understanding of how many actors act. Not all actors "feel" the emotions of their characters and reflect deeply on them. Some simply say the lines and are able to portray the realistic characterization they need to without deeper attachment (Michael Caine is famous for this). It may be worthwhile asking how the judge prepares for his roles.
Finally, there is a question of whether audience members know enough to separate the judge from the characters he plays or the things he says onstage during a comedy routine. Again, we should take into account cognitive v. emotional processes (although it's never as simple as 1 v 2). Cognitively, most of us will understand that character is not the same as actor. But emotionally, we may still have a reaction to the person standing in front of us. If for no other reason than we associate the person physically with the character.
Alas, there is no real psychological research (yet) on whether actors are actually affected by the characters they play (either emotionally or cognitively), whether creating a character or enacting a scripted character causes different reactions in the actor, and whether and how adults are affected by watching a real person play a fictional character. The question of emotional reactions v. cognitive reactions will be a critical one going forward, and should be of concern when deciding this judge's fate.