Alright, so here's a thought: Long ago, we had a program granting a sort of half-mod status for users called Ferrets. We could possibly bring back this program for the purpose of policing community tags, if it will make the idea less contentious.
An idea of how I see this possibly working, just as an example: Community tags are invisible until approved by a Ferret, who have a FIFO tag queue (possible prioritization could be given to a specific subset of "problem" tags, or tags added by multiple users). Content owners don't receive a tag notification until Ferret approval, and unapproved tags are tossed unnoticed by anyone, and possibly reported for administrative action if they are abusive in nature.