So if the judge can compel an oath under penalty of imprisonment that requires one to violate his jury responsiblity, is the jury simply window dressing?
No, the jury is the trier of fact, and determines the credibility of each witness. They apply the facts to the law that they are given.
Note the original post above. The case apparently turned on the credibility of the witnesses.
Let's use copyright law as an example. You and I would probably agree that the current law is badly in need of reform.
Now, if I was called to jury duty, I'd be able to set my views aside, and determine the case based upon the current law. You might not be able to do so. But would you admit that up front, or would you lie about the fact so that you could get on the jury and subvert the law. That's the moral choice that only you can make.