How could john newton reconcile his christian faith with his career as a slave ship captain?

As a slave ship captain, John Newton would read passages from the bible and often used it as a basis to do punishment to the slaves.But over period of time, John Newton realized the devastating effects on Africans and started to take a stand against it. He began to spread a lot of anti-slavery pamphlets in his hometown in his fight to abolish it

The second one one is

Indian removal was a forced migration in the 19th century whereby Native Americans were forced by the United States government to leave their ancestral homelands in the eastern United States to lands west of the Mississippi River, specifically to a designated Indian Territory (roughly, modern Oklahoma).
Target: Native Americans in the eastern United ...
Date: 1830–1847
Location: United States