My hunch is that you are doing this to remove tags that are assigned to files? I can see how that would work; however a bit manual for hundreds of tag and files spread over the file system. FYI, process Crap load of tags might be easier for lots of tags.
I’m at the point where I want to remove tags that are NOT assigned to files but still show up in the tag list. Able to do this manually with the Finder Menu: Preferences, Tab: Tags EXCEPT when the tag holds certain “funny” characters (which I suspect are related to Regular Expression codes).