以子之矛，攻子之盾　

◎ 以子之矛，攻子之盾 yǐ zǐ zhī máo,gōng zǐ zhī dùn

[Turn sb‘s battery against himself;Fight sb.with his own weapon] 用你自己的矛来刺你自己的盾。比喻用对方的论点来驳斥对方