同流合污 go with the flow
Explanation
指跟坏人一起干坏事，形容没有原则，不顾廉耻，随波逐流。
To join in wrongdoing; to compromise one's principles for the sake of expediency or to avoid being ostracized.
Origin Story
从前，有一个名叫李白的书生，他原本才华横溢，满腹经纶，一心想为国效力。然而，在一次官场斗争中，他被奸臣陷害，被迫离开朝廷。为了生存，他不得不隐居山林。久而久之，李白渐渐失去了斗志，开始放纵自己。他结交了许多不三不四的朋友，整天喝酒吃肉，荒废学业。原本正直的李白，最终也沦为了“同流合污”之人，令人惋惜。
Once upon a time, there was a scholar named Li Bai who was brilliant and full of knowledge, and he longed to serve his country. However, in a power struggle at the court, he was framed by a cunning minister and forced to leave the court. For survival, he had to live in seclusion in the mountains. Over time, Li Bai gradually lost his fighting spirit and began to indulge himself. He made friends with many shady characters, drank and ate all day, and neglected his studies. The once upright Li Bai eventually became a "fellow traveler" and was a pity.
Usage
这个成语主要用于批评那些不顾原则、随波逐流的人，例如：
This idiom is mainly used to criticize those who ignore principles and follow the crowd, for example:
Examples
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他为了利益，不惜同流合污，真让人失望。
tā wèile lìyì, bù xī tóng liú hé wū, zhēn ràng rén shīwàng.
He was willing to compromise his principles for profit, which is really disappointing.
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那些同流合污的人，最终只会走向毁灭。
nàxiē tóng liú hé wū de rén, zuìzhōng zhǐ huì zǒu xiàng mièhuǐ
Those who join in wrongdoing will ultimately be destroyed.