why give amnesty?

I personally feel that the South shouldn't have been granted amnesty. I understand that Lincoln thought by granting amnesty to the South that the North and South could be together as one, but lets face it, this is reality not everyone is going to agree with him . Then because of him granting amnesty to the South the effect ended up being that many people in the North were angry at him. Who wouldn't get angry ? Especially the North who just finish loosing love ones in this chaotic war. Although Lincoln was trying to do what he thought was right , northerners  probably saw it as a bad thing because in other words they fought a war and lost love ones for nothing if hes just going to forgive the south and act like nothing ever happened.