Racial slurs are racial slurs.
Spic is short for hispanic and nigger comes from negro, but that hardly makes them acceptable to use unless one is doing so to make a point.
I’ll also be honest and say I find it rather dubious that someone from India was unaware that the term “Paki” was a racial slur.
That strikes me as being about as plausible as claiming that someone from Texas was unaware that “spic” was a racial slur not just a shorthand way of saying “hispanic.”