Currently this is not possible. It's indeed an avenue for abuse that users will take advantage of.
Another factor of this is that it needs to be visible who created or added a tag, so that it's possible to address abuse with the member.
Sometimes members abuse the tagging functionality to add hateful or abusive tags to content. Or to a specific user's content within the context of harassment.
It would be useful if we could blacklist abusive tags and also if we could see who added the tag and when.
Reporting a tag should be possible.