Hmmmm!...ethnocentrism. I certainly agree that an element of ethnocentrism exists in China. Is that another reason native speakers are preferred here? Possibly, in some cases. I do think though that this debate (sorry discourse!) is splitting hairs somewhat, because of the following points.

Ethnocentrism, as the name suggests, in China (and of course everywhere else) does not extend to just Japanese people, blacks, and non-native speakers of English (as you indicated yourself when you used those groups as just an example), but to ALL foreigners including native English speakers and whites. If ethnocentrism plays a significant part in the school selection process then surely those establishments wouldn't want to employ any foreign teachers at all. In any case ethnocentrism cannot be such a big issue because there are still many schools in China who are willing to employ non-native speakers.

So the questions are: Do you think ethnocentrism in China is extended to all foreigners in China? If so do you really think that it plays a big part in the selection of foreign teachers (native speakers and non-natives) if they are being frantically sought all over China? If ethnocentrism is a significant reason for native-speaker preference why are many non-native speakers happily employed in Chinese schools up and down the country?

I think the REAL reason for native-speaker preference lies elsewhere.

Thanks for the discourse!