It is the context that the word is used in that is offensive. When the Pakistani cricket team tour Australia they can be referred to as Pakis without offence because it is part of Australian vernacular to abreviate nationalities like that with no offence intended. When the same players tour England there is no question that Paki, if it is used, is used as a deliberate term of abuse.

Being called a bastard in Australia is practically a term of endearment. There is a famous story about Douglas Jardine, England cricket captain in the 1930's, taking offence at being called a bastard on the field of play and demanding an apology after the game from the Australian captain. The Aussie said "fair enough" and turning to his team-mates called out "which one of you bastards called this bastard a bastard".

Chink is still a term of abuse in England, I certainly wouldn't sing a song containing the word.