Decent people have had their lives ruined by his behavior.

decent 是形容词，由词根 dec-（源自拉丁语 decere，意为"得体、合适"）和形容词后缀 -ent 组成。基本意思是"体面的、正派的"，引申为"正直的、品行良好的"。 在句中指那些品行端正、为人正直的人。