Obviously other tags are misused by people unfamiliar with the mathematical concept they tag under.
Many times an advanced user will leave a comment, explaining the question is mistagged, and ask for clarification for the tag being used, and possibly retag as well.
Most of the newcoming users accept this understandingly. However, some may not.
How far should we insist on proper retagging? What proper course of action in case of a user rolling back, and insisting the question is not wrongfully tagged? Some of the time these questions and users are under heavy fire for badly posing the question (or it could be completely off topic to the site), these things only worsen the ability of the user to admit their own mistake and accept the retagging.
Even if closed, I do not think a question should be tagged improperly. Since retagging always bumps the question there is no point in retagged discarded and closed questions. Deletion might be good for some, but for other questions serve as a lantern for future discussions to refer to and need to be kept around. What do we do in this case?