I am thinking of it as a message from the writer to the user, and doing so gives me a little chuckle as I remember there is a human on the other side of the code that makes my server run.
If you write code for yourself then that's one thing, as soon as you write code for potential distribution to a large audience (cron is present on just about any unix machine) then I think you should restrain yourself from trying to be funny (or at a minimum from having your software by proxy call people names).
Call me old fashioned, it just doesn't work for me.
On the other hand, IMO, the biggest profanity you can put in an error message is an error code and nothing more. Now THAT is how to mistreat your users!
I wonder if there were similar discussions about the insults sudo gives you on OpenBSD (http://prefetch.net/blog/index.php/2012/08/01/sudo-insults-w...)...