Even if you work for New Jersey government (transit)? John Eastman, among others (Eugene Volokh), disagree, in a New York Times symposium. No Heckler's Veto--especially if you're not on duty when the stupid act was done.
[H]ow far are we willing to let the threat of violent reaction to peaceful speech and expression go when it is used to curtail First Amendment freedoms? Suppose that Fenton had simply held up a placard (or a cartoon!) defending Israel and chastising those who launched mortar attacks against Israel from the Gaza Strip as the latest round of Israeli-Palestinian peace talks were getting under way? If New Jersey Transit thought that might provoke attacks against its trains, too, could Fenton be fired for that as well?
Governor Christie's heroic efforts to rein in spending may be for naught if New Jersey has to pony up for the firing!