123everton, I quite agree that a spade and a shovel are 2 entirely different implements and perform 2 entirely different tasks, but the expression I mention is well established. The OED has "colloq. phr. to call a spade a (bloody) shovel: to speak with great or unnecessary bluntness", with citations from 1919 on. At least nobody can credibly say that the spade in this is anything but an agricultural implement. Perhaps it's you and I who are in for a very long day!
Your (actually quite affectionate) Chinese term for foreigners is the Cantonese 'gwai lou' (roughly gwy-loe). The corresponding Mandarin term would be 'guǐzi' (roughly gweydzz). 'Foreign demon' is 'y�ng guǐzi'. I would agree the latter terms really are offensive.
Gentile is actually a definition by non-creed or non-race, isn't it? One of beso's neg defs.
Kuffar is an outright obscenity. It is simply the plural of kaffir, which is bad enough whether used by S Africans or Muslims, but once again it's the associations that make the difference, for me at any rate.