If black unity and ultimately black liberation are only about securing power, privilege, and the well being of straight black cisgendered men than there's nothing to stop elite blacks from exploiting or being tyrants over other black people. Not to mention the injustices and mistreatment heaped on black women and black LGBTQ people.
We are not perfect because of our blackness or experience of racial injustice. If we don't recognize that then we will replace white racism with black tyranny in any kind of liberated social, economic, or political setting. Look no further for proof of this than the all the authoritarianism that has characterized so much of sub Saharan Africa since the end of colonialism. Look at the strife and instability in Haiti.