>t's a bit like calling someone a "chinaman."

The Talmud speaks of an Etrog "Hakushi" to describle a black Etrog (Jewish ritual fruit). Not necessarily one that comes from "Kush".

"Kushi" is not more a slur than "Black". That is to say it is NOT a slur, although it CAN be used in a negative fashion when used in a sentence in conjunction with stereotypes associated with the black community. It all depends on the context of what is said.

It is totally not resembling "chinaman" in the context of it being used for describing negative stereotypes associated with the term. Though it is also not like "englishman" which is usually used in connotation with positive stereotypes.