Let us not seek to satisfy our thirst for freedom by drinking from the cup of bitterness and hatred. We must forever conduct our struggle on the high plane of dignity and discipline. We must not allow our creative protest to degenerate into physical violence. Again and again, we must rise to the majestic heights of meeting physical force with soul force
Sumner was physically attacked by Brooks in Congress because "<span>d. Sumner challenged the Fugitive Slave Act and angered pro-slavery supporters" since he was an avid abolitionist. </span>
After the war, the Radicals demanded civil rights for freed slaves, including measures ensuring suffrage. They initiated the various Reconstruction Acts as well as the Fourteenth Amendment and limited political and voting rights for ex-Confederate civil officials and military officers.
You will have to look at whether or not the creator of the source had a really positive or negative outlook on the situation.
If they are -for example- great friends with a bully, they will not tell as much of the truth, but if they are enemies, they may tell a very exaggerated truth to get them in trouble.
You must look for a very neutral feeling on both sides of the matter. If the author has an opinion, more likely than not it will affect the way they share the information