Also that's no racism, that's simple reason and i would think about it the same way, if it would be a buyer from Uruguay or Kyrgyzstan

It maybe isnt racism but its xenophobia for sure. Im just wondering where you draw the line.
Anything beyond Texas? USA? English speaking countries? Northern hemisphere?
There are legitimate reasons to be cautious of dealing with people from Nigeria. The country has a sad story, you should read up on what happened there in the 90s.