How would they proof that the original comment wasn't libel? I doubt the have cross refrenced commenters IP addresses with the numbers listed. And if you relay libel (especially with malicious intent) it is still libel or maybe even blackmail.

And if I recall correctly, they might even be required to prove that they have opt-in permission from the actual users for storing&processing their personal info (phone numbers) even if they obtain it from a third party such as other websites; they obviously don't have this so they can face fines for improper treatment of personal data.