Danielle Staub is being sued for $5 million by ex-husband Kevin Maher, who says her allegations of rape and other insults against him are defaming.

But Staub has now taken legal action in return, making the same case THG makes any time Larry Birkhead sends us a letter complaining that we're harming his reputation via a few negative articles: you do that all on your own, pal!

In documents obtained by TMZ, Staub says Maher has "no evidence" that Danielle said anything especially bad about him. Moreover, even if something did slip out of her mentally unbalanced mouth... so what? Maher has already stuck a foot deeply into his own.

In "Cop Without a Badge," the book that exposed Staub's drug-dealing past, Maher admits to the following:

• He used cocaine.
• He has "overactive sexual proclivities."
• He once shoved a gun into the genitals of a man he thought was banging Danielle. 

For once, therefore, Staub might actually have a point: how can anything she says defame the reputation of a man that has already owned up to these actions?

If Danielle and Kevin cannot work out a settlement, the latter's lawsuit will go to trial in February.