A Stick to Beat With

a stick to beat somebody/something with (British)
something that gives you an excuse for criticizing someone or something that you do not like or approve of .
These evangelical types had set up store on this bench. A mobile trolley containing pamphlets placed by their side. This guy with the shorts and cloth cap turned up and they were both intrigued by his stick. I say it was a stick but it looked a bit more awesome than that-like a Shillelagh. Perhaps they saw its potential in getting a view across!