I only really know him from the movie American Splendor and his David Letterman appearances, but I agree that he was a working-class hero:
Pekar used his few minutes of fame to bring national attention to striking stage hands and abuses of NBC’s parent company, GE, to light. He was truly heroic because he did not think of himself. He could have went on being an amusing character for Letterman, he could have gotten his own TV show (maybe). All he had to do is not speak out. But he didn’t keep silent, maybe he couldn’t. Instead he took a principled stand for all to see.
Pekar’s characters, much like himself, were the ordinary people, working people, of Cleveland who struggled so hard just to get by. Unlike them, Pekar used his talents as a writer and creator to make visible these struggles, therefore turning art into politics. He will be missed.