No it isn't, I wish people would stop saying this. They're two different words. You can find "nikka" offensive but it doesn't carry the same weight as the hard "er"
Not coming at you, but why/how are they different words? Where in history did the "a" and "er" definition differentiate?
Different race says "a" = we all flip out

Seems like the same weight to me.
Why is the "a" ok? Past it being a different context that I always hear people say