Steve Rubenstein’s working life after the Chronicle has involved a lot of time lounging around with college students. He’s been teaching a course in magazine writing at San Francisco State University, where such illustrious Chronicle alumni as Yumi Wilson and Harriet Chiang also teach. Last week, Rube forced his erstwhile Chronicle associate and current Guild Executive Officer Carl Hall to join him for a talk that wound up focusing on one of the fundamental principles of journalism: “You have to care,” Rubenstein said.