It all started with Daisy Dizzy, who asked (via email, less than 24 hours before class) for an excused absence in order to "eat a quick lunch" and pack before traveling to an elective student "competition" AS AN ALTERNATE. As a matter of course policy, absences due to elective student activities, much less eating or optional travel, are not excused. Moreover, the impact of missing class was nil because students can miss 4 without penalty. My mistake was detailing course policy for her via email less than 1 hour before class AND cc'ing the faculty advisor to the student club. The faculty advisor saw the unreasonableness of the request and instituted a professional conduct policy for student competitions and club travel. That was a good thing, imo. However, this student (and all the club members -- 4 of which were in my classes) knew the policy was a direct result from my email & discussions with the faculty advisor. From that point on, Ms. Dizzy and her minions were a nuisance in and out of class for over two months.
In a way, I have to thank Ms. Dizzy. I've made changes to my course policies and my MO: I only respond to student email during office hours (usually with "see me to discuss" or "take a look at page 3 in the syllabus and see me if you have questions"), I don't excuse anything but bereavement and serious illness per university policy (which means athletes are now SOL in my classes), and students will be graded on professional conduct in all classes (10% of final grade).
But the biggest lesson I learned from Daisy was this -- Sometimes, simply ignoring students is the best option.