I have been told that the main reason is the government (and increasingly national) animosity towards Zambias asian population. Just like the situation white Zimbabweans have been thru, the Zambian government is using their asian population as the "bad guy", in order to avoid having attention drawn to their own failings.

If I have understood correctly, the majority of Zambian concessions have been in asian (mainly Indian?) hands. So a ban is the perfect way to "stick it to them". The Chinese are in the Zambian dog house too, with quite a few of them being the victims of murder and other violent crimes recently.