Just sent me a rage email about how I should take my graduate studies seriously or I will never get my thesis and how my absences are unprofessional. Well, joke was on him because I dropped his class over 2 months ago and had he re-printed his roster he would have seen that. I responded and told him the professional thing to do is check your roster everyday so you do not send vague threatening emails to students that are no longer your students, and to have a wonderful day.