Most English teachers (ESL included), are neither grammarians nor linguists.

Your lack of understanding of double negatives is obvious to any genuine English teacher reading your posts.
ESL teachers with genuine TESOL certification credentials must study grammar.
English teachers with genuine education credentials routinely teach grammar.
Both groups of teachers will understand the definition of and proper use of double negatives.
There is no linguistic debate about double negatives. One need not be a grammarian nor a linguist to understand this basic grammar point.
Your continued dialog is "caught in the cookie jar" obfuscation.