Couple minor points:
Lincoln served one term in the House during the Mexican War. He was never in the Senate.
AFAIK, Lincoln while in the House did not submit any bill regarding colonization. If you have evidence to the contrary, I'd be interested in seeing it.
It would not be surprising if you had never heard stories of blacks abused on your family's plantations. Even before the war, such abuse was not widely publicized, if only because slaveowners knew it would be used to attack the institution.
After the war, former slaveowners had every reason in the world to minimize the brutality of slavery and its importance to the Lost Cause. They even developed the theory that secession and the War hadn't been about slavery at all, the exact opposite of what the same people said before and during the war.
Colonization was widely popular, including in the Upper South in early 1800s, among people who considered slavery an evil but didn't know how to safely get rid of it.
It was essentially a way for people who wanted to get rid of slavery to avoid the issue of how black and white people could live together in peace and equality after emancipation. Give the problems we're still having 150 years later, they appear to have had a point.
We shouldn’t forget that Lee was a big proponent of voluntary emigration as well.
Stand corrected. While serving in Congress.