People did speak against slavery they were called abolitionists. These were people like Oladah Equiano and Frederick Douglas. These people wrote books describing the awfulness of slavery. I also suggest you read Harriet Teacher Stowe's book Uncle Tom's Cabin. This was a direct look into the Horror of slavery.
There was never anything that said they couldn't speak against slavery in public.
quakers :} im pretty sure
Slavery
Quakers were among the first in England to speak out AGAINST slavery.
The most prominent group of people that spoke out against slavery were the antebellum group that was termed anti slavery abolitionists. They were very outspoken and received allot of attention in the newspapers of the day.
The first known individual to speak out against slavery was St. Augustine, a theologian from the early Christian Church who argued that slavery was a result of sin and was not part of God's original plan for humanity.
slavery
The first trip Frederick Douglass took to Britain to speak out against slavery was in 1845. He remained in Britain for about a year and a half.
Yes, Sojourner Truth did travel the country to speak against slavery. (I know because I need to know this for a History paper)
The Quakers were among the first religious groups to speak out against slavery in the United States. They actively campaigned against the institution of slavery and were instrumental in the abolitionist movement.
Sojourner Truth
Slavery