Sojourner Truth and Frederick Douglass were both former slaves whose reputations as abolitionists were both built on speaking about their lived experiences as slaves.
It may seem obvious now, but in order to support abolishing slavery, people first had to accept that it was wrong to enslave people. A common claim among proponents of slavery was that slaves were well-treated and happy. Truth and Douglass directly contradicted that claim by reporting things that they personally had lived through or witnessed. For their work as abolitionists to be effective, it was essential that they be believed.
As far as Truth and Douglass were concerned, the stakes could not have been higher. By the time their public speaking careers started, they had their own freedom, but there were still countless enslaved people in the South. If they were somehow discredited and the Abolition movement suffered as a result, it would have meant a blow to the hope of freedom for all of those people.
