Firstly, I am not a trained linguist and secondly, neither are most of the teachers here.

So, from my 'non-linguistical' understanding, what you are saying is that a sentence containing 2 or more of the same scopes of negation is grammatically wrong. If not, then how can grammatically correct sentences containing double negatives exist in the same way as non-grammatically correct sentences exist?

Ooh, phone call, sorry.............wo budebu zuo - lol