I don't know that there is a method to do it completely anonymously, but the fact we're even treating the mere operation of an exit node as a crime, and something to be hidden at all costs, is a rather depressing indictment of the current state of our legal systems. Ideally one should be able to proudly and publicly make a stand for anonymity - that's where my comment about a decent amount of money comes in. A higher profile name who sets up a (charitable?) organisation with limited liability (not a perfect protection, but something) and loudly announces to the world how they're standing up for the First Amendment rights of all Americans (or some local equivalent) makes for, at worst, a protracted and public case in which the government can easily come out looking like the bully.
It's imperfect, certainly, but plenty of people have made the world a better place in the process of being fucked over making a stand against their governments. Many others have won. Some have disappeared into the legal system for all eternity. Sometimes the sacrifice is in vain, sometimes it isn't, but it almost always packs a better punch if you have the money and publicity to manage it well.