to knock the competition 诋毁对手（非正式用语）

英文释义

To make insulting, disrespectful comments about one's competitors in business, or their products (NOTE: this is a negative, unethical practice)

例句

The insecure salesman tried to knock the competition by saying that their employees were stupid and unreliable people who could not find work anywhere else.

这位无把握的销售员试图诋毁竞争对手，说他们的员工愚蠢而不可靠，在别的地方根本找不到工作。