Just Say No
"I'm sorry, while we are normally able to meet such requests in this specific case we are unable to provide a character or performance reference. However we can confirm $PERSON worked here from X to Y."
We all know what this means. Why would you need to say anything else?
The only fathomable reason I can see for giving someone a reference that is both negative and detailed is if it was given by a senior manager (i.e. rather than HR) with an axe to grind.
Biting the hand that feeds IT
