This is War(man)!
... Still, the defence seems fairly straightforward to me:
The above-named posted the allegedly libelous material, not because they intended themselves to defame Mr. Warman, but so that they could tease-out and expose that Conspiracy of Defamers whom we all know lurk malignantly in digitally darkened corners, just waiting for an opportunity to discredit the only man in Canada who can tell us what right and wrong are.
Warman could even testify for the defence as to whether or not he believes that such means justify the ends.