On my daily ride to work there is an image, the "No" symbol (red circle crossed by diagonal red line) imposed over another, a woman in a burqa, and captioned "Say no to burqas". The image is painted on the side of a building, at a street corner on a quiet street which faces the train line.
When it first appeared it was of course controversial and the papers wrote about it, but it stayed and has been there for quite a while now.
This morning, however, I glanced up at just the right moment to see it flash by, and in that instant saw that the image had been defaced by what looked like a tin ful of white paint being thrown at it, obliterating most of the image and streaming down the wall and across the footpath and into the street, and beside the defaced image (or the modified image, or the improved image, or the amended image, depending on your point of view), there was a man writing in uneven, bright red letters, "FREE SPEECH"...