Shaun (and whoever else)-

Here is the explaination you asked for.
listed in this order:

country(noun)- of the country(adjective)- person from that country(noun)

Britain- British- Briton(endearing abv.= Brit)
Thailand- Thai- Thai(there is no abv. There is also no such word as 'Thailander')
Japan- Japanese- Japanese(derogatory abv.= Jap)
Pakistan- Pakistani- Pakistani(derogatory abv.= Paki)

It is about language and communication not a maths equation. It is not consistant in the way you suggested.

Being British I understand know that many British people don't consider the term 'Jap' to be offensive (although those people often don't know any Japanese people personally) but many do find it an offensive term.

However, undoubtably, that term is usually considered to be a strong derogatory term on a world scale. This is an international forum which calls for international savvy.

There are Japanese people that read this forum. There are also some people on here, such as Matt and myself, who have Japanese relatives and friends.

Maybe you don't mean it in a bad way but at the end of the day is it really important for you to keep using the word 'Jap' on this board when worldwide it is considered to be a racial slur?