Earlier quoted context omitted.
Do you know what the lawyers said beyond "I'm a lawyer and would like you to edit the blacklist" ? Are these companies doing something illegal by blacklisting you unfairly, or do you have grounds for some sort of civil suit (if so, what grounds)?
I would think "Tortious interference" is the most likely legal basis to complain about it. "Tortious interference is a common law tort allowing a claim for damages against a defendant who wrongfully interferes with the plaintiff's contractual or business relationships"
A blacklist is not directly interfering with your business. They just provide a list that contains IPs, your IP, and say we have seen spam traffic from it in the last x hours. The mail receiver, who trusts and uses the list might be interfering, but it is his right to pick and choose who he is accepting email from. Same right you have to pick and choose who you let into your bar, apartment, club, house, ... what so ever.