Don't forget; these b*stards really may have NO right to make demands of you. They probably CANNOT touch you. And they ceratinly have no right to expect you to respond to such vague accustaions. What if the police stopped you and said, "We didn't see you drive the last few miles, but we know you broke some laws, so we want you to write down all of the laws you broke, and we'll write you a ticket!"
Bullsh*it! They can't make you do that! If these guys have a legitimate beef, they can be specific. I think you'll find they haven't any songs 'they own' in your database. i think you'll finf they formed their company, and they wrote thousands of generic (mis-spelled) letters to every organization they could think of, in order to get annual dues. They don't really protect artists like us.