Well, I'm not a programmer, and can't think of any better solution than the ones you have proposed. But I totally agree with you that we should deal with this. Incorrect tags (among others) are to be fixed as soon as possible.
Here, in this post I explain why we should fight (I say flag, because that's the only way I know of, right now) spam, and at the end of the post I link @neoxian's good post about what to consider spam (including tag abuse).
Hope you'll have a take, and maybe some way to help :)
Have a good weekend,
sharingtheworld