Martin Gayford uses the incident of teacup and the Mona Lisa as a pretext to talk about other cases of art attacks. His catalog tends toward the acts of insane persons but on occasion he finds a vandal or two with a “higher” purpose:

Consider the case of Mary Richardson, the suffragette who cut up Velazquez’s “Rokeby Venus” with an axe in the National Gallery, London, in March 1914. Not only did Richardson have a just cause — votes for women — but her action was part of a campaign that included other attacks on paintings and setting fire to buildings including railway stations and country houses. She was no lone nut-case but part of a movement. Most people today, I suppose, would support her aims though not her methods. There’s a myriad of explanations for this kind of high- profile vandalism ranging from moral disapproval — Richardson disliked the way male visitors ogled the nude Venus — to thwarted artistic ambition.

Mona Lias Teacup Attack Joins Looney Tradition of Defiling Art (Bloomberg)