Call me British not a Brit because that's a racial slur. What rubbish. Japs is just short for Japanese as Scots is short for Scottish. You may prefer the extended version but it's not a racially loaded slur. Some people just want to stir up racialism where it doesn't exist.
Twithay?
Yes I agree we have to be careful because some abbreviations have negative connections associated with historical events. In the instance you refer to I believe that in the sixties that Pakistan's shortened name was joined to a violent term for assaulting people. This abhorrent term now, justifiably, determines that the shortened form of Pakistani is racially loaded. Similarly the use of "gay" was originally associated being happy, happy and gay. The word has progressed from that to being used as an insulting accusation of homosexuality, and now is accepted as part of modern sexual designation. So, yes I totally agree we have to be careful because there is always some one or group looking out to be offended, even if…
With regard to shortening the nationality, we have to be careful sometimes. British to Brits, Scottish to Scott and Australians to Ozzies is fine. However, a Pakistani national won't appreciate the trend - and nor should he.