[ben_w]

To be blunt, the public obviously includes people suffering from paranoid schizophrenia delusions that make them believe they are an ambulance[0] and therefore "drive" into a painting where someone is injured in order to rescue them or something.

Or bored kids with crayons will try colouring it in and/or peeling off gold foil[1] if it has any, or well meaning idiots will try to restore it like that Jesus picture, or a hundred other things because the public isn't just the best of us, it's all of us.

If art isn't protected, it will be damaged. Failing to take preemptive defensive measures against predictable threats is not as blame-worthy as the actual proximal causes, of course, but it's still blame-worthy.

[0] I've met someone who had to be sectioned after something similar made them think they were a car and therefore started walking along the middle of a lane.

[1] I've witnessed that.