The group responsible for putting up that billboard has had it papered over:

The phrase “radical leaders prey on the fearful and naive” had been plastered at the bottom of the billboard yesterday. Ryan Rhodes, chairman of the Iowa Tea Party movement, says the billboard was counterproductive.
“It’d be great to have a billboard that’s really actually helpful, that’s not demonstrating fear but demonstrating freedom and that we have solutions and goals,” Rhodes says.
The North Iowa Tea Party paid to put up the billboard in downtown Mason City, drawing criticism — including criticism from others in the Tea Party movement. Rhodes, the chairman of the Iowa Tea Party, hopes the new blank slate that’s now in that spot could be put to better use.
“It’s got to be more than just the initial shock/fear value,” Rhodes says. “What we need is something that accomplishes our goals because our goals are about helping people understand and educating them about our nation’s founding and the path bath to American exceptionalism.”