Two, and more to the point, the complaint ignores the fact that after 50 years or so of freedom from colonial powers, African nations defend those borders:
Several African states are worried that the imminent independence of South Sudan will lead to a radical redrawing of African borders. Libya has stated it openly, but everyone knows the fear is shared by many African governments. Colonial powers drew most of the borders in the 19th and 20th centuries. The borders-drawn-in-parlors often divided tribes and sometimes made very little on-the-ground geographic sense. If South Sudan votes for independence (secession the northerners call it) the thinking goes that this will cause a chain reaction, first in the Grand Sahel (Darfur being another possibility) then throughout the rest of the continent.So they hate the imperialists for drawing the borders, blame the borders for their ills--but don't want to risk opening them up for discussion.
Practically speaking, I'm sure few people in Africa would mind it if their oppressed brethren on "the wrong side" of an artificial border were brought into the loving and respectful protection of their own country. But how many countries would accept the loss of territory to let their people go?
African nations either need to work on ways to adjust those "bad" borders if they are really that imprtant to making progress, or stop complaining about them and formally accept them--and then do their best to prosper within their existing borders.