"When you send a message, your client must first compute a Proof of Work (POW). This POW helps mitigate spam on the network. Nodes and other clients will not process your message if it does not show sufficient POW. After the POW is complete, your message is shared to all of your connections which in turn share it with all of their connections."
So not only does this not help with abusive behavior, it states that abuse will live forever and be impossible to block or filter.
/me shudders
You have the right to say anything you want (though not without consequences). Conversely, I should have the right to literally not see/hear it once I've decided it is causing me harm.
Claiming that your platform/protocol makes this impossible just sounds naive at best and nefarious at worst to me.