Is there an English metaphor/saying for this expression?

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.

This idiom does exist in English:

it is easy to find a stick to beat a dog

It is easy to attack (physically or verbally) a vulnerable person or thing. Primarily heard in UK.

I know it is easy to find a stick to beat a dog, but you need to stop criticizing your son—he's not being malicious, he's just a child!

https://idioms.thefreedictionary.com/it+is+easy+to+find+a+stick+to+beat+a+dog