The idiom 众口铄金 originates from ancient Chinese texts and reflects a deep-seated cultural understanding of the power of the collective. In a society where social harmony and reputation (面子 - miànzi) are paramount, an individual's standing is heavily influenced by public perception. This idiom serves as a stark warning against the dangers of groupthink and public shaming. A useful Western comparison is the concept of “trial by media” or “cancel culture.” However, there's a key difference. While Western concepts often focus on the media or social media platforms as the medium, 众口铄金 focuses on the raw, elemental force of the unified human voice itself. It suggests that when enough people say something, their collective speech becomes a force of nature, capable of bending reality, regardless of the technology used to spread it. This ties into the cultural value of avoiding public confrontation and protecting one's (and others') social “face.” To be the target of 众口铄金 is to have one's social existence fundamentally threatened.
众口铄金 is a formal and literary idiom. You won't hear it in casual daily chatter, but it is frequently used in more serious contexts.
The connotation is almost exclusively negative. It is a lament or a warning about a destructive, unjust force.