Can Art and/or Poetry Be Harmful?
Art and poetry can most definitely have harmful effects on humans. From slanderous caricatures to mind-numbing propaganda, art and poetry can contain concepts and ideas that are maladaptive and disruptive.
Anti-Semitism was rampant well before Hitler and the Nazis came to power in Germany. These sentiments were created and spread using caricatures and fallacious histories. Jews were blamed for all manner of ills, and were described as being evil, scheming, conniving, disreputable, etc. Racism in the US was spread in a similar manner. African slaves were commonly depicted as inferior than white landowners, and Native Americans as ignoble savages. These perceptions persisted in no small part because of their prominent depiction in cultural outlets.
Art that compels people to violence, such as propaganda, is also detrimental. Compelling videos of brave soldiers battling for the safety and well being of the home country, stark war posters suggesting a grim but unavoidable task, and portraits of the great leader that brings victory can be deployed together to change the outlook of an entire nation, stirring millions of people to violence. It glorifies death and destruction (of the enemy); behaviour we would normally strongly discourage in our nation now becomes sanctioned and organized. Television advertisements (including shows) operate in a way similar to propaganda. They motivate us, as a nation, to purchase goods in obscene quantities, well beyond any reasonable or responsible need.
In these examples, the underlying point to be made is the connection between forms of expression and what ideas they actually express. Racism makes for harmful art because it is a harmful and divisive idea. Blatant and nationalistic propaganda connotes obedience to authority and to the group (no matter how corrupt), appeals to drives of domination, and stresses sacrifice and the glory attained from it. Television trains humans to perform a disconnected act of exchange.
This is not to say that all art is harmful. A medium cannot be inherently adaptive or maladaptive, moral or immoral; as with fire, it is more how we use art as a tool than art itself that is harmful.