Answer:
mob mentality
Step-by-step explanation:
The other options are symbolism, theme, and rhetoric. They don't fit because of the rest of the excerpt since "they preferred to think and act independently". It has nothing to do with the other options but it is the clear opposite of a mob mentality, which is how it is described a collective behavior based on the idea of one's behavior being influenced by everyone else's in the mob instead of rationalizing the situation.