Right, so you apply the Dalton principle: be nice. When (not if!) they ask you if you will follow instructions and law, then, and only then, nicely, tell them that you believe in the principle of jury nullification, and that you cannot promise such a thing in good faith.
Of course, IANAL, and what exactly you encounter will depend on the other people present as well as those doing the selecting, so whatever happens from there will depend a lot on the human factor. You should, therefore, only do this if you truly believe it (as I do). Trying to get out of jury duty is shirking your responsibility, but telling the truth, and getting out of it because it is the truth, is not your problem.