Cultural expression, righting a long-standing wrong, doing God's work, a step up from standard vandalism, downright bloody-mindedness, sociopathic epidemic, wickedness, or what?
Regardless, what is the remedy for this kind of thing - can you suggest one, or is it up to authority to deal with it in the own ineffectual way. Why would it not get steadily worse, the contamination spread, perhaps exponentially, rather than dissipate over time of its own accord?