If you could witness some of the most gruesome, painful and mentally scarring moments that took place during slavery: the rapes, the murders, the whippings, the being forced to nurture and raise the next generation of oppressors etc.
If you could witness a few moments of those, would you still look them slaves in the eyes, call them “nigga” and then tell them it was a term of endearment? Do you think they’d buy the theory of “we’re changing the meaning?” With that “change” comes the loss of the history. The loss of the struggles and the pain that those that were enslaved fought to get rid of.
We are no longer slaves, not physically or legally anyway (though mentally some of us are still debatably enslaved) so it is no longer our word to “change.” We should focus on “changing” ourselves and our image, not a word that carries history behind it.