Here is a searing, hot take from an unstudied amateur:
On the surface, the symbol of Christ's cross and the invention of the word 'nigga' had similar intentions: to re-purpose a negative (word, symbol) into a positive and free a people.
Yet the massive difference between Christ and all other identity movements throughout history is His divinity and God's love. These two crucial components cannot be duplicated. Without them, identity movements inevitably sharpen the divide among common people, regardless of their good intentions.
In the first centuries of the United States, both black slaves and free blacks were labeled 'niggers' by whites, with the purpose of objectifying and oppressing them.
Fast forward to modern times: Segregation is unlawful and blacks are free citizens with the right to vote.
Some blacks believe there are still controllable economic and political disparities that need addressing. Various social movements and leaders emerge with strategies ranging from peace to civil unrest to achieve these goals.
By the '90s, these movements culminated in the cultural 'gangsta' rap sub-genre, the success of which was due to the appropriation of the indisputably offensive slur for pop use (aka profit). Gangsta rap became a phenomenon. To this day some of these dated albums and songs are considered 'classic' by white, suburban music nerds.
The new diluted slur, without the infamous "Hard 'R'", was meant to liberate those from the ugliness of the real word by allowing them a form acceptable for use among themselves, as a term of endearment. It didn't uplift marginalized people from poverty; it was popularized by entertainers posturing as gang members and criminals, and made real people proud to live in conditions of impoverished crime. It was a middle finger to "oppression," while itself stereotyping the ethnicity of people it was attempting to uplift!
Educated blacks from good neighborhoods didn't use or condone use of this new slang, but their skin color unfairly grouped them in with these gang affiliated entertainers.
In my opinion, the word nigga was invented to sell another manufactured crisis of inner city black identity as it became "our word." The word is now so commonly used in rap that it is a watered down slur of a watered down slur. Light skinned hispanic rappers use it in their own songs! (Though it is not "their word" historically, hispanics are allowed to use the word with each other because they are also minorities in inner cities! (Whites can never use that word. Not even Eminem.))
Before Christ, the cross was a symbol of the painful death guaranteed to dissidents of the Roman Empire. After Christ sacrificed himself on the cross and suffered an excruciating death, re-purposing the sign of the cross as a blessing was itself a guarantee of the same death by the Roman oppressors.
Only the divinity of Christ's love could convince the faithful to exchange the meaning of the cross from a symbol of excruciating death to a symbol of hope and resurrection. Only the prayers and devotion of the faithful living in Christ could do that.
The cross is a symbolized miracle; a miracle that was intended for all of those living and dead, not just those of a certain ethnicity. Only God has the power to turn the most horrible form of torture into the universal symbol for love. Selling crosses was not their purpose.
The word 'nigga' was created in spite for history itself. True, blacks were lynched and beaten, but today the people living in government sanctioned poverty and throwing "their word" around are liberated only in their disrespect for themselves and their ancestors. Furthermore, there is no universal acceptance of the word 'nigga' or else everyone, regardless of color, would be "allowed" to say it.
Just make the sign of the cross! And don't use ethnic slurs, even in karaoke!
Everything leads back to Christ.