Eli's got the goods. I finally caught up on Mann's points to dismiss Steyn's counterclaims and Steyn's response - haven't read Steyn's original motion though.
Interesting that Steyn found some actual lawyers to double down on his claims rather than tell him "we'll represent you but only if you drop these stinkers." There are powerful corporate interests that don't want to be sue-able for things they say or allow others to say on their websites, so there could be corporate law firms that will represent the "can't sue us!" side.
I agree with Eli - the arguments are still stinkers. My guess is the lawyers are in it not for these claims (unless they've really fooled themselves) but for the longer game of beating Mann's suit.
On the first claim that an anti-SLAPP law provides an implied right of action, I think first that would've been discovered somewhere before, and second, the implied right, if hypothetically true, would exist for anyone who'd been SLAPPed. Sounds unlikely.
As to the second claim that a protection against government also applies to a private person using the court - yes Eli's right that this makes any lawsuit a state action.
The third claim of tortious use of litigation sounded theoretically plausible until I read it - they just made it up, because the common law theoretically allows that to happen. This goes to the question of when people laugh at you, what's the probability that you're Galileo versus the probability that you're Bozo the Clown.
How many wholesale revisions of the law did Steyn invent?
The value of this stuff lawyers made for Steyn is that it seems novel to me, and saying your claim is novel is a decent way to fight against the argument that it was frivolous and therefore subject to sanctions. OTOH, if Mann wins his anti-SLAPP motion then it doesn't matter how innovative Steyn's lawyers were.
One final note - if I were designing the law, I would of course allow a motion to dismiss ridiculous counterclaims like Steyn's counterclaims. I would not, however, allow an anti-SLAPP motion just over a counterclaim made solely against the fact of the plaintiff's original filing (I would allow it if the counterclaim dealt with something else). Having said that, if I were Mann or his lawyers, I would use that tool if it were available to me. They assert it is, and I don't know the law well enough to judge that.