To be unreasonable and refuse to listen to reason; to act in a crude and stubborn manner.
态度粗暴，不讲道理。
毛泽东《关于正确处理人民内部矛盾的问题》在我们社会里，也有少数不顾公共利益，蛮不讲理，行凶犯法的人。”
He was so angry that he became completely unreasonable, refusing to listen to any explanation.
Learn the next connected idiom: 蛮不讲理 (mán bù jiǎng lǐ) → 理所当然 (lǐ suǒ dāng rán)
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