It’s a known authoritarian practice to undermine the meaning of words: in this case, applying the word pornographic to an artistic masterwork representing a biblical figure in the nude. At the same time, they are diminishing the cultural and historical value of art; art and history are threats to them that must be suppressed for their narrative to reign.
Il David is an important work to study in European art history, and frankly any curriculum that omitted it would be questionable.
Nudity is not the same as pornography.