Unfortunately for those of us who really have to go, many students use the 'bathroom ploy' to get out of being called on. I had two profs who made it policy that bathroom breaks were not allowed, ever! (and both profs were female, and stated female issues might work for the male profs, but not for them)
Officially, our school requires every case be briefed as part of class preparation. This policy is largely ignored by the profs under 50, and enforced by the older profs.
As far as being late for class, yes, your prof is overreacting > because he can. His mindset however, is that a client, a court, and a firm/public entity will expect you to be punctual and prepared. Before fire laws took effect, some profs would lock the doors to the classroom at starting time. Keep in mind, if you think he is an egotistical jerk, wait until you're in front of a judge > particularly the over 50 crowd. Your prof may be doing your class a favor > particularly those going into criminal law (criminal law judges are inherently insane) or civil litigation.