How did Congress try to get southern plantation owners to let their slaves join the Continental Army?

Africans having pride in their own culture despite being ruled by people of different cultures gave them a sense of self worth.

Explanation:

The people of Africa were ruled by people of different cultures and by the people from different countries. They had a history of colonial rule where they were a colony of many countries.

But despite being ruled by people of different cultures, the people of Africa had pride in their own culture. This gave these people a sense of self worth. The Africans had pride in their own culture, in their own language and their own nation.