guilt by association

An assumption of culpability due merely to one's association with a particular person, group, or thing. In reality, the CEO had nothing to do with the scandal perpetrated by the company's Chief Technology Officer, but it's seen as guilt by association in the eyes of the public. The popular Internet forum was never intended to serve as a platform for extremism, but guilt by association has set in over the years due to the increasing prevalence of such views being published and shared there. A: "Why are you in trouble? You weren't even involved with the prank." B: "Guilt by association because I'm the captain of the team."