A good read:
http://www.torys.com/Publications/Do.../LDR2008-5.pdf
I don't think there's any way Wenzel's suit meets this threshold.
(For those who won't read it, it essentially says that Nenshi's statements don't need to be true, nor does Nenshi need to believe that they are true... they only need to be things that one could rationally believe to be true on the basis of things that are true - and to me, they certainly meet at least that bar.)