I spent 11 years working in a black oriented church (Glide Memorial) where I worked closely with many ordinary black street people, including bums (especially when I built Drunk Park on 6th and Minna) and several black professional peers.
What always surprised me, though it shouldn't have, is that blacks of all stations (not Africans or blacks born outside the U.S.) had gigantic holes in their knowledge of how the white world works.
While the black street person's knowledge of political ways and often technology was usually accurate, their knowledge of business, finance, civil legal and academic worlds was spotty, often inaccurate and sometimes imaginary.
To find a black who didn't know how businesses uses credit scores, how commercial leases work, the elements of bookkeeping, tax laws on dividends or how to buy stock in a foreign company was much more common than in the white community.
Two reasons for this. About one third of all urban blacks arrived from the South in the 1950-60s, many of the rest came during WWII. So all issues of urban life are fairly new because the assimilation into urban middle-class has been slow over the past sixty years for blacks.
Also, if you don't live in a predominantly white community, you don't know what it is that you don't know about the white world. Instead you get reinforced in your views and experiences by other black people who also lack such experience.
Next time you have trouble with a black person, as with all people, be polite consider first that you may be at fault, but secondly, remember that assimilation has been slow and the black person may not know what is customary in the white world.