There's a difference? Seriously asking.
As a serious response, how well do you know the American (or Western) political system?
It works like this
On the far Left you have Anarco-Communists ---> Anarchists/Communists ----> Marxist-Socialists (Traditionally) ---> Democratic Socialists -----> Green Partiers ---> Democrats ("Progressive" wing) ----> Democrats ("Moderate" wing) ---> Moderate Republicans ----> John Birch/"Tea Party" Republicans -----> Libertarians
Plenty of interplay and the like in-between, but they Black Leftists and Black Liberals have starkly different goals.
The Black Panther Party had a decidedly Maoist focus, they didn't just want "equality" for African-Americans (and People of Colour, focusing on the radical East Asian and Chicano groups at the time), they wanted liberation from capitalism as a whole, alongside from racism, misogyny, nationalism, etc.
They also were developing an ideology that focused on African-descended peoples, were they not essentially terrorized by the US government, they had an international vision.