The question, IMO, is what the consequences of your lack of respect would be. If you actually express your contempt out loud, you could end up in the slammer, since contempt of court is one of those limits on expressing your opinion, despite the First Amendment (there's a time and place... which is not in court). A limited expression of your contempt could lead to being dismissed for cause. There is actually some chance that you'd be dismissed for cause, if the judge asks about any prior entanglements with court – you do not want to perjure yourself and pretend that e.g. no member of family has been subject to court proceedings.
The basic legal question is whether your attitude towards the judge will influence your behavior as a juror. The judge will tell you how to decide the case, which means you have to actually follow his instructions. You can't (or, are not supposed to) just make up your own definition of "aggravated assault" or whatever the chargeis, and if the judge says that you must disregard something that a witness said, then you should do that, rather than think "Who are you to be telling me what to pay attention to and what to ignore?". If you can't follow the judge's instructions, you are supposed to simply say that you believe that the judge is scum and you can't take him seriously, and you will be excused. If you don't tell the truth about your attitude, and they find out (not hard to do), there could be serious consequences because you lied about one of those questions about whether there is any problem with you following instructions, or however they ask it.