I don't understand this statement: "Blacklisting based on the /64 won't work, due to the potential to deny service to legitimate users," At the moment, we have

I don't understand this statement: "Blacklisting based on the /64 won't work, due to the potential to deny service to legitimate users," At the moment, we have multiple users sharing a single IPv4 address, so when that gets listed, there is collateral damage. If we change to having lots of users sharing the same IPv6 /64 and we start listing /64 there is no change to the collateral damange... If every user starts getting their own /64 to send mail from, then this will reduce the collateral damage, but make it harder to list. In which case, larger blocks will get listed, again bringing the collateral damage back up to the same level we already have it at...