Ummm that would be kind of... illegal.....
Great idea! Be sure to alert the media so that they can be sure to catch your great act of stupidity er..defiance for the six o'clock news.
Like I said, CitizensUnited.Org needs to have video cameras trained on those billboards 24/7.
Guess vandalism is OK, though, when you damage the property and restrict the free speech of conservatives.