My hunch that the letter to the editor by the two San Francisco school board members was cut for space turned out to be right. artnet news has the complete letter. It does not expand on the malarkey discussion, however. Here's the full section:
"When one makes their way to the end of her commentary it’s not shocking in the least to find that she makes a false equivalency argument about students potentially being triggered by viewing photos of the My Lai massacre. Malarkey."
The main thrust of their argument remains the same.
The position of the open letter writers is: a work of art should not be destroyed if its message is anti-racist, even if it is traumatizing to students.
The position of the school board members is: a work of art that is traumatizing to students should be destroyed, even if its message is anti-racist.