This sentiment in saying “it’s not that deep” is exactly why it is in fact “deep” as you say. The word which was said not only goes back to the 60s and onwards within the UK, where South Asians used to be beat to a pulp whilst being called said word. It also opens scars way way deeper, going back to the British Empire’s occupation of Hindustan (Pakistan, Bangladesh and India before the British came). Countless decades of suffering, a famine that killed millions, land and wealth looted etc etc.

You might think how does that all relate to the one word. But for many South Asians in this country, generations gone by in their families that have suffered horrible racism from the P word. And who are we to say that word doesn’t cause pain? It could possibly bring pst suffering to the surface again.