I think the contempt shown by "leaders" is not solely towards foreign teachers but also towards local staff as well. The working conditions in china are generally poor and the way that management treats employees would often be seen as unacceptable if you were to compare any industry in china with the equivalent in the west. Perhaps the contempt towards foreign staff appears more evident because we often expect better treatment having just arrived from countries where it's the norm. Local staff on the other hand are often happy to lie down and take it as they've never experienced anything different. Of course you could argue that we as foreigners often do receive better treatment than locals in terms of wages, benefits and working hours which in itself contributes toward the contempt.

I fully agree with silverboy that learning Chinese should not be a prerequisite to being treated fairly by an employer who has employed you primarily on the basis of you being an English speaker. However, I do concede that in reality learning the language has many benefits for an individual.