a stick to beat someone with
US /ə stɪk tə biːt ˈsʌm.wʌn wɪθ/
UK /ə stɪk tə biːt ˈsʌm.wʌn wɪθ/

1.
誰かを打ち負かすための棒, 攻撃の口実
a piece of information or an argument that can be used to criticize or harm someone
:
•
His past mistakes became a stick to beat him with during the election campaign.
彼の過去の過ちは、選挙運動中に彼を打ち負かすための棒となった。
•
Don't give them a stick to beat you with by admitting your weaknesses.
自分の弱点を認めて、彼らにあなたを打ち負かすための棒を与えないでください。