I considered that, but it's difficult to prove the owners, you can only make an informed guess. Also, it makes it too personal, much as the Avalon Project would deserve to be blocked from spending their Bitcoin.

Blacklisting the greenlist works better. We can prove these people are trying to destroy the principles of security^1, fungibility and privacy for all Bitcoin users, sigining up and using this "service" is all the proof needed. And we also have no idea as to their real identities, we just have a list of sanitised public keys. We must organise to prevent transactions either from or to these green addresses from being processed by miners. They want to create a plague that infects all non users of their system, we can take their list and use it against them. Instead, they will be the sufferers.

¹This is a genuine concern. The more frequently an address is used, the easier it is for an attacker to compute valid signatures to sign transactions made from that address (knowing the private key is not required). This is one of the reasons it is discouraged to re-use addresses. The more valid signatures in the blockchain that exist made from a single address, the more information the attacker has to work with.