Reviewing through your description, I ran through a local test by adding tags to documents via the bulk content management feature, however was not seeing the same message displayed.
As such, this could be a permission based behavior. For clarification, if the user navigates directly to the documents, are they able to add tags to the content?
Either way, I would also suggest submitting a case in your customer group ( MyJive Secret Support Group Administration FAQ ) as a next step so that a member of our support team can review through your instance specifically and confirm if you are running into a bug. When submitting the case, if you could include the username of the account seeing this behavior, along with a link to the place where they are attempting to add tags, this should assist with their investigation.