Do you understand the difference between black as a race and black as a cultural group? Blacks were identified by their race under the law, which just homogenized and marginalized them in American culture, hence the whole notion of black identity. There is no need to have "white pride" because there are many distinct cultures within that group. And those cultures usually break down into region (e.g., Northeast, South) or country (e.g., Italian, German, Polish, French). Black culture has primarily southern roots, for obvious reasons, and "black pride"and uplifting the community should be seen in the cultural sense. It can also be seen in the racial sense because it is a group that was told it was inferior during the eras of slavery and segregation (even after).
When you ask why these concepts such as black pride come about, don't ignore history. White pride is seen as racist because why would you need to elevate a group that has been privileged in American society for all of its history? Elevating it higher would mean other groups are below you; in contrast, elevating the black community would be to have a group elevated to equal status because despite what is said on paper and in our laws, it's a group that has been held as inferior throughout American history.
However, with the increase in Caribbean and African population, black identity has certainly changed and I see a shift towards African American identity pointing its cultural roots towards the descendants of those from the South (just my view of course).