Unfortunately during that era blacks were for the most part considered to be "property" and not human beings.
When the Declaration of Independence was drawn up in 1776;
"We hold these truths to be self-evident, that (all men) are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness"
The above statement was not intended to apply to slaves and Native Americans.
It wasn't until August 18, 1920, the congress ratified the 19th amendment providing guarantees all American women the right to vote. Therefore not even white women were seen as equals.
The Supreme Court didn't legalize interracial marriage until 1967.
Historically you look back and wonder how so many injustices could have be allowed or perpetrated by government of the people for the people.