The library names are unnecessarily sexual -- "Hardon Collider", "AnAL", "LUBE", "Polygamy"...
"Why should I have to censor myself for anyone?"
"It's a free country."
"I'm so tired of this politically correct society we live in."
"I'm a woman and I love dick jokes!"
And so on.
"Heh - it's called Hardon Collider - I should show my friends how funny this is!"
I'd wager that they think the group of people who will find this funny and share it is larger than the group of people who will find this obnoxious and avoid it. "And who cares about those uptight assholes, anyway?" In the end it becomes a very sad, tight feedback loop for these kinds of weird sexism.
Online communities with a significant number of very young people tend not to be the healthiest ones.
The examples Scaevolus lists are all in there.