I met a group of several people who were very persistently trying to put a floppy disk in a CD-ROM drive. They refused to listen to my polite explanations that it just doesn't go in that slot. They tried for half an hour, and I think they broke the CD-ROM drive at some point.

Ignorance is understandable. I'm ignorant about all sorts of things. But what I don't get is willful ignorance.