He's suing them for slander.

他控告他们口头诽谤。

《牛津词典》

This will put them in slander.

这会使他们陷于诋毁。

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Article 25 Business operators may not insult or slander consumers, may not search the body of consumers or the articles they carry with them, and may not violate the personal freedom of consumers.

第二十五条经营者不得对消费者进行侮辱、诽谤，不得搜查消费者的身体及其携带的物品，不得侵犯消费者的人身自由。

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