No, kat, I wasn't equating anti-Irish racism (of which there's a fair amount about in some places) and racism towards black people. The fact that it's easier for Irish to "pass" is only part of it (my son told me that at one time at school he would let people think his name was Scottish), there's a different history to it, and a different resonance.

And part of that is reflected in the way that terms like "Paddy" and "Mick" can actually be used in a friendly way. This means that just going for the term itself isn't the answer here - you've got to read the intention behind its use, and that is more complicated.

With "nigger" there is normally a racist intention out in the open. But the same intention can be trailed by people in formally inoffensive ways. The important thing is to identify the racist intention, whatever words are being used, and react appropriately. (If sometimes the same words were being used without a racist intent, maybe in a historical context, or perhaps by a foreigner, a quite different reaction might be appropriate.)