How were Frederick Douglass, Henry Highland Garnet, and apparently David Walker the strongest arguments for abolition

Because they all proof of the degree of impacts a free slave or colored person can have on society, by showing how blacks and whites should be equal

Explanation:

Frederick Douglass was an escaped slave around 1838 and later went on to become a prescher or advocates of slavery abolitionist throughout his entire life. He also lived an upstanding life.

Henry Highland ld Garnet also escaped slavery around 1825, and later became an abolitionist who used his entire life to seek the end of slavery. He also lived accordingly without committing crimes.

David Walker was a freed colored man who out of empathy for colored people like him, used the rest of his adult life to seeking slavery abolishment. He died in 1830 believing it could be as a result of anti-abolitionist at the time.

Hence, Frederick Douglass, Henry Highland Garnet, and apparently David Walker are the strongest arguments for abolition "Because they are all proof of the degree of impacts a free slave or colored person can have on society, by showing how blacks and whites should be equal."

the answer is use of support  

which time period is this? or is this story fictional, i'm going to need more info to answer this question