Jurors are registered voters and free citizens of the United States. There are many reasons voters can be excused from service and serving under a judge they do not feel comfortable with should be one of them. To me, not agreeing with the judge might actually be an incentive to serve in an effort to mitigate what might be undesirable trial results, but if someone doesn't want to serve under a particular judge they shouldn't have to. It is still supposed to be a free country.
No, jurors may often disagree with a judge they are assigned, but it is important for them to make due with the situation they receive and not to let a judge they disagree with ruin the entire case. It is their responsibility to try to get the judge to see eye to eye with them so that the right verdict can be reached and so that the sentencing can match said verdict.
Jurors should not be allowed to refuse to serve under a judge they disagree with. If anything, they are further preventing justice being served by removing their perspective from the trial. I don't see why jurors would even want to refuse to serve under a judge they disagree with; it seems like this is the time when it would be most important for them to have their perspective present.
I couldn't imagine letting a juror out of juror duty simply because they do not agree with the judge. This would be far too easy of an excuse to use to get out of serving, which is something that many people would take advantage of. There is a reason that jury duty is mandatory, as nobody wants to really do it.