When population of a country like Ethiopia exceeds the level that can be sustained by their agricultural production, and still the population growth continues fuelled by the international aid, it is a problem for distinct reasons:

• The country will be dependent on aid. A policy change on the side of the donators could cause famine, and the country's government could be easily blackmailed and become a puppet of their sponsors.
• We aren't successful in helping African countries to develop more efficient economy today. After their population doubles, it would be even more difficult.
• There is certainly some limit which the population couldn't surpass even with the aid of aid. When the population reaches that limit, we can expect famine, war or massive emmigration. Those would happen sooner without the aid, however in smaller scale, because the population would be smaller.

One can hope, of course, that somehow Africa will become developed and the population will stop growing enough soon. But there is little evidence that this will happen. The kind of aid which supports population growth doesn't solve the problem of poverty. It only postpones the solution while the problem is growing in scale.