It's not a racist issue. It's an experience and finacial issue. The ex-pats have not had their ex-pat allownces included in their contract renewals, so they've been saying "bugger this - I'm off". Their replacements have been new ATC controllers on local contracts which of course mean local Chinese controllers.
The big problem is, these newly trained controllers don't have regional airports to cut their teeth and gain experience. They're thrust striaght into the deep end - as if a new ATC cadet in the UK has been put stright into the approach controller's position at London Centre instsead of working his/her way up from Norwich tower. It's not the controller's fault. Blame the system that put them there, and the managers whose main aim is to save money.
At the end of the day, you get what you pay for. In this case, safety is being compromised to fulfil a budget.