DMCA is for copyright infringement, not defamation. That's not to say it doesn't get abused in all sorts of "we want you to take X down" scenarios, however.
For safe harbor here, you'd be looking to the CDA, I believe. In that case, what matters is the level of editorial control you exercise over the site. The complaint alleges that they review every comment before posting, which if true, would seem to be a problem for them. My understanding of the CDA is that, somewhat perversely, you're better off having low standards than high ones with respect to user-submitted content.
That aside, the above is a layman's understanding of the relevant law, not legal advice. If you're ever in a situation where this information is important, please discuss it with a lawyer.
For safe harbor here, you'd be looking to the CDA, I believe. In that case, what matters is the level of editorial control you exercise over the site. The complaint alleges that they review every comment before posting, which if true, would seem to be a problem for them. My understanding of the CDA is that, somewhat perversely, you're better off having low standards than high ones with respect to user-submitted content.
That aside, the above is a layman's understanding of the relevant law, not legal advice. If you're ever in a situation where this information is important, please discuss it with a lawyer.