This has never made any sense to me. "People are dumb, panicky animals" because "people" is made up of "persons" who (in aggregate) dumb stuff down. The individuals in the "people" are also "dumb, panicky animals," generally speaking.

It's just speaking to the idea of pack mentality. It's ingrained in us to go with the flow because we're a social species. So, if someone else makes a mistake, it's not nearly as bad if we make a mistake as well. On the flip-side, if you're the only person around, you can't rely on anyone else and it forces you to think about things.

It's not always true of course; just a colloquialism.