a stick to beat someone or something with
stick to beat (someone or something) with
Something, often a mishap or misdeed, that is used as an excuse for criticism. Even the slightest mistake by Stan was enough to give the boss a stick to beat him with.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
a stick to beat someone or something witha fact or argument held over someone or something as a threat or an advantage.
Farlex Partner Idioms Dictionary © Farlex 2017