I think he meant derogatory.

He definitely meant defamatory, since he apparently tacitly threatened suing the Liberal Party. But whether it’s true or essentially a SLAPP threat is unclear.

It’s certainly possible that he believes the report contained factually incorrect non-opinion claims about him. I can’t see that being likely though. I guess the fact that they didn’t give him the opportunity for a right-of-reply in the report can’t have helped. That would have given him an opportunity to address any potential issues before it got to this point. It really seems like a monumental fuck-up on their part not to have contacted him for right-of-reply.