tar people with the same brush
tar (someone or something) with the same brush
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. There is absolutely a segment of video game enthusiasts who create a hostile and toxic environment online, but tarring all gamers with the same brush does a disservice to the community.