Race vs. Nationality
The bottom line is that most people consider derogatory racist labels to be far more offensive and hateful than derogatory national labels. You may not agree with that (indeed it sounds like perhaps you do not), but the fact remains that this distinction is the key consideration at play in most of your examples. People have all kinds of reasons for that they may tend to dislike people from a certain country. These reasons will generally be based on stereotypes that are often false, but they are not racist. Aussie, Kiwi, Yank etc. are all based on the nation one comes from, not one’s race. Even a more derogatory term like “frog” would not be subject to the same level of scrutiny, because it has nothing to do with race.
The term “Paki” is clearly more about race than about nationality
You raise an interesting example with the word “Paki”, and I think this example illustrates the point. There are, no doubt, some very small number of blond-haired, blue-eyed Pakistani citizens. Do you think that the word “Paki” would be used to refer to these rare Pakistani citizens if someone saw them on the street? I submit that if you are honest with yourself you will answer in the negative. How about someone from India who immigrates to the UK? Any chance that person might be called a “Paki” by some drunk idiot on the street? Of course they might (and are). Why? Because it is a derogatory term that is used as an insult against people who have certain physiological traits that set them apart visually.
An Explanation, Not an Argument
To be clear, I am not trying to persuade you here that derogatory terms referring to race are inherently worse than derogatory terms referring to nationality (I happen to think that they are, but that’s its own debate). I’m just explaining that most people do feel that way. This distinction explains why, for example, people can write books about why they hate the French, or why they hate Americans, and those books are accepted in mainstream society, whereas a book about “Why I hate black people” would never be touched by a mainstream publisher. Most relevantly for our discussion here – this race vs. nationality distinction is the reason that racial slurs are specifically prohibited by the Forumosa Rules, and “country slurs” are not.