Personal opinion,maybe I'm wrong on this,maybe not...
Do NOT remove anything hosted in RBN netblocks for the time being,
no matter if domains get temporarily cleaned/shut down -> to HELL with all of them.
If they are indeed legitimate webmasters with no malicious intentions whatsoever,
well then,they should choose different web space providers -> simple as that,heh...
Hope to hear other people's opinion on this matter...