This isn't banning books from the school library, teaching whitewashed history, or destroying works in a museum, it is a painting on the wall of a high school.

...one that doesn't seem to have any particularly strong artistic or historic value outside the controversy over itself.

Let's be honest, it was a communist painter trying to be edgy or subversive. Art is important but people are overinflating the importance of painting. Picking up a brush doesn't infinitely elevate what you have to say.

At best it's sarcasm painted on the wall, at worst propaganda in any case hard to justify as an appropriate wall decoration for a high school.

There are worrying trends of the left trying to force its morals and opinions with government, but this isn't the best target for that criticism.