Which value may be defined as, 'the willingness to stand up for what one believes to be right' even if that stand is unpopular or contrary to conventional wisdom?

This value is called moral courage. It happens, for example, in a case of a deliberate action/stand of a person who is fully aware of the risk or possible (negative) consequences, and still does that action or takes that stand. It is a highly nonconformist trait, seen in individuals who place truth or common good above their own interest.