In American high school I learned not just about Nathan Hale and Martin Luther King Jr., but also about Nelson Mandela, Mahatma Gandhi, and Sophie Scholl. These figures are famous for the strength of their moral beliefs, the brutality they endured as a result, and their perseverance despite such adversity.
On these points, I think Liu Xiaobo is of equal merit. This would explain his visibility in the West. If students in China aren't taught similar stories or values, then I could understand the difficulty to relate.