Two members of the Tea Party, Gregory Luce and Nicholas Newman, decided that a highway overpass in Campbell, Wis., where Interstate 90 crosses the Mississippi River over French Island, was a good spot for their “Honk To Impeach Obama” banner. But their protest violated a content-neutral ordinance enacted by the town legislature based testimony from the police chief, Tim Kelemen, about safety hazards allegedly caused when motorists saw signs, flags and banners on Campbell’s three highway overpasses.The …