Native born English speakers have been in rigorous training since they were two months old.

ABSOLUTELY RIGHT!!

We know the accents and the subtle nuances which Sasha from Serbia or Samuel from Ghana cannot possibly ever know. Part of language is exposure, and non native speakers have just not been exposed to it in the same way. Just like as foreigners, we can never know every dialect or nuance in China. A native speaker without a degree, should be allowed and welcomed to teach if he/she wants to in China, even if just at kindergarten level, end of story, full stop, period as the yanks call it!!!!!