I'm translating a book and the author has written down a saying that can be translated literally as "If you want to hit a dog you can easily/quickly find a stick" Like, if I wanted to hit a dog, finding something with which to hit it will be easy as I'll be looking for anything I can to injure it. It need not necessarily be a stick, but just some kind of weapon...
The meaning is if you're already predisposed towards hating something you'll quickly find a way to destroy it.
If nothing like this exists feel free to say that and I'll try and find a way around it. I'd rather not shoehorn in an awkward translation.