You using the phrase "Most Paki's" is polite company should earn you opprobrium.
In not so polite company, physical chastisement is the very least of what you should expect.
You've been told twice now, so you've no excuse, but, carry on with the butter wouldn't melt routine.
Interesting.. I'll take the word of the many Paki's I know over yours any day. There's a lot of them living here, the family who own the corner store down the road for a start will quickly say "We're Paki's, not Punjab's" (they do intend the latter as a racist comment).
"Paki" means "Someone from Pakistan" all over the world. Just like "Kiwi" and "New Zealander" mean "someone from NZ" etc. To claim it is "racist" is quite wrong, especially when the people themselves use it as a term to identify their heritage.
You have, however, repeatedly threatened violence against me for using a term people I know wish to have used to identify their heritage. Not only are you yourself actually being quite racist (doubly so as 1) you credit them with being unable to speak up for themselves or unable to make their own choices about identity terms and 2) you have no idea about my culture and wish to impose your will on it), but you are also committing what is in many countries a criminal act. One could even claim you're inciting terrorist activities by saying it should be "prolonged violence" or "physical chastisement is the very least of what you should expect".
What do you think you would face if you were in NZ and saying these things? Under our current climate, to seen to be promoting racial terrorism (even if that wasn't your intent) and worse to be doing it based on a term those you claim it is against actually use themselves very happily?
Carry on with your own routine, but that won't make you any more right.