Many people even in the South held the same views on the Negro race as did Lincoln, and also thought that Slavery was a bad practise. But it was a matter of LAW, agreed upon in a Repersentative REPUBLIC form of government, that owning a slave was just as much of a right under the Constitution as the owning of a gun. In fact even more so because it was written into the body of the Constitution rather that being attached later in the form of a specified amendment to that Constitution. That is the reason the 13th Amendment had to be added to the Constitution to repeal that specific clause. The 13th Amendment is the ONLY amendment that a War had to be fought over in order to get it passed. WHY?
Lincoln WAS controversial because of his views on the POWERS of the FEDERAL Government. He was what we would call today, a "Progressive", and believed that the FEDERAL Government, and he as President, had the power to superceed the Constitution and suspend the rights of States under that Constitution to self governance, based solely upon his election as President of the United States. And that election was not even by a majority of the people. That is NOT a "REPUBLIC" form of Government idea. That is a "DEMOCRACY" Ideal, even dictatorial ideal, that an elected Official with the backing of the Majority, or not, has the "RIGHT" to rule of a minority. An elected Offical authority and power, even for a President, comes from the LAW, NOT an election.
Our Forefathers knew the dangers of a "Democracy". England had been a "democray" under Parliment and King George III. Our Forefathers established a "Republic" under which 3 branches of Government acted independently of each other to check the abuse of power by any one single branch of that Government, and untimately that membership within the Union of "United" States was voluntary, subject to the will of the people within each States and that no state was to be subjected to the oppression of any of the other States.
Lincoln changed the way this country was governed. That is why he is STILL controversial. Yes, he may have caused the slaves to be "freed" as a political price that had to be paid to create the "new" Government of the United States that was to follow. But what was destroyed? What did we as a people lose, for that "new" system of governance to be created?