This blog post reports of an interesting encounter: that a student at NYU's business school was shopping for classes and entered a business prof's class an hour late; he told student x to come back on time the next class; student wrote letter saying that x was just jumping in and out of class on the first day to shop and didn't know the rules; prof wrote long email explaining that manners, humility and such were basic requirements and the easy stuff one should master if one wants to succeed.
And I say: hell, yeah! I tend not to have the guts to take strong stands since I am soft and squishy, but I hate, hate, hate with a burning passion when students leave class early. I tend to expect folks to come a bit late (although an hour late would set me off), but leaving early really distracts me and my students. I used to have my TAs at TTU chase down early leavers to get their names and dress them down, but that proved to be a big distraction.
If I were really smart and teaching a big lecture class, I might actually game it so that a fake student comes by very late, I kick them out, and then send around an email like this. Not saying this event is fake, but it is almost as good as a friend of mine who stages a cell-phone call at the beginning of the term which leads to a planted phone being throwing somewhere.
Anyhow, I find the entire story plausible even if some folks on twitter do not: entitled student, outraged but articulate prof, email that digs the hole deeper and then counter-email which edu-micates quite well.