Been there, put up with that. I'm surprised by the idiocy on a particular teacher's listserv. Exact same crap from time to time. One of the better ones was when someone offered to send a CD via regular mail & said "reply off the list with your mailing address." Dozens upon dozens of idiots replied with "I'd like a copy of the CD" (no mailing address.) And, those replies were quoted and replied to over and over again with "Me too! Thanks!" The response to that was exactly as you described... every other email was someone wanting the CD's, and the replies in between were politically correct, friendly attempts to get people to reply off the list and actually follow directions. A couple of us discussed the whole situation privately & off-list & came to the conclusion that there are a some tech-illiterate teachers out there who can't even figure out email.
The worst case was when one person replied to the entire list, and that person's coworker thought it was just sent to themself. That person replied with an "oh, by the way..." and a bunch of very confidential information. The original fool replied back with more confidential information. It went back and forth for 4 or 5 emails before the inbox filled up with everyone replying to those two morons (and the entire listserv) that they were sending their confidential messages to 100's of people.