IANAL myself; but it seems like some form of safe harbor provision applies here at a minimum. Tor (the organization) itself isn't even operating the network; they just write the software that other people then use. It's like suing Adobe in a defamation suit because someone used Photoshop to put your face on a porn star's body.

Edit: After reading the rest of the suit, this is clearly a frivolous suit. The entire filing is pretty unprofessional overall; hopefully the EFF can step in and stop this nonsense.