Africans resented colonial rule for numerous reasons. One was that their land and resources were being exploited which destroyed the land. Another was that they were being enslaved by the white people. Another was that there was an oligarchy where the few rich white people ruled over a vast majority of Africans and exploited them in every possible way.
The Federation of Rhodesia and Nyasaland was a federation of African territories which was a semi-independent British colony. Nowadays, the countries are known as Malawi and Zambia and Zimbabwe. It was ruled by white people even though the most white people ever that were there constituted only 3 percent of the population.
The arguments for federation were that they stabilize economy and help the land prosper which wouldn't be possible without things like trade and economic advancements and technological development. They also helped Britain through trading since they would be a colony that worked with them often.
The arguments against it are mostly revolving around the general anti-imperialist ideas. They were exploiting the people in mines and getting wealthy at the expense of the population. They were also destroying the area through heavy exploitation of the land and stripping the people of the natural resources while at the same time violating human rights.
As the time passed on, the sentiment of African nationalism started spreading more and more and people form the area started fighting for independence. They eventually managed to win it and turn it into the three countries that were previously mentioned which would be governed by the locals.