“一竿子打翻一船人”，中文俗语，意思是因为对某人或某物不满意，就否定和他们类似的人或物。与英文俗语“tar somebody/something with the same brush”意思相近，表示“to unfairly categorize someone or something as being the same as another person or thing, usually in a negative manner”。
Just because the CEO turned out to be a rotten scoundrel doesn't mean we should tar the entire company with the same brush.
My buddy thinks that I shouldn't ask Joan out because she's divorced and he'd dated divorcees who seemed desperate. But I'm not going to tar her with the same brush. It isn't fair.