Wrong. Unqualfied native speakers withouit relevant degrees and proper teaching
qualificatuiojns do the harm.
Can you explain what an accusative-cum-infinitive structure is in English? Poor students that
you will "teach".....

It's to do with objects in transitive verbs. Don't make this a pissing contest about who knows more grammar; as has been proven many times, yours is not flawless and you hide any mistakes behind this 'descriptive' grammar nonsense. Getting technical is pointless considering anybody with access to this forum presumably has access to google also.

Non-native speakers with relevant degrees do just as much harm as unqualified native speakers. What one has in applied knowledge (a non-native speaker who has studied English will most likely understand the terminology and mechanics more) they other has in fluency and the non-native speaker will make frequent mistakes in pronunciation and grammar that a native speaker will more often than not not make.

As I said, non-native speakers should have to attain a C2 Proficiency level certification in English and even then should only be allowed to teach up to A2 level, in order to minimise these errors. Native speakers without qualifications should only be allowed to teach conversational English, as they do not have the knowledge to answer questions about the whys and hows of the language, that L2 speakers need in order to gain certification in English.