This is a passage from one of Ted-ed articles. I think both 'placate' and 'benign' have a positive meaning respectively while 'unthinking stupor' has a negative implication. The sentence doesn't make sense to me. What does the sentence mean?
One of the most important applications of music in Ancient Greek society is found in the belief that music can affect a person's ethos. A word we still use today, ethos is a person's guiding beliefs or personal ethics, the way that one behaves towards oneself and others.
The Greek philosopher Plato, one of the most famous and influential Greek thinkers of the time, asserted that music had a direct effect on a person's ethos. Certain kinds of music could incite a person to violence while others could placate a person into a benign, unthinking stupor.
According to Plato, only very specific types of music were beneficial to a person's ethos. One should only listen to music that promotes intelligence, self-discipline, and courage, and all other kinds of music must be avoided. Furthermore, Plato fervently denounced any music that deviated from established musical conventions, fearing that doing so would lead to the degradation of the standards of civilization, the corruption of youth, and eventually complete and utter anarchy.