From all my readings and knowledge of some of the people you describe it falls into 3 broad categories.

1. You have the "Lost Cause" camp who through no real fault of their own were brought up in parts of the South which still holds to the virtue of their cause, and in Lincoln's roll as agitator and war monger. They then attribute all the destruction brought by generals like Sherman and Sheridan to Lincoln.

2. You have those who object to Lincoln's less then strict interpretation of the Constitution especially early in the war. In Maryland he had sitting elected state representatives arrested so that they could not even debate succession. This included 1/3 of the state legislature and sitting Congressman. They were held as political prisoners.

Lincoln additionally suspended the right to Habeus Corpus in Maryland along with declaring Martial Law, while the state was still part of the Union and of course never did succeed. What that meant essentially was that a person could not challenge the fact that they were detained Unconstitutionally or where not being charged with a crime and simply held in jail. While the US Constitution DOES include a provision for suspending HC during times of insurrection it is found in the Article enumerating the powers of Congress not the President.

When the Chief Justice of the Supreme Court ruled that Lincoln was acting unlawfully and that HC was not within his power to suspend he simply ignored the ruling and ordered the army to continue the arrests and holding the prisoners.

Not quite what you want in a President who is nominally fighting to uphold the supremacy of the Constitution and the government based on it.

3. And Finally you have your assortments of racists and bigots which should need no explanation.

Without adding too much to the previous poster, the primary reason by which I disregard Lincoln versus say Jackson on the use of Executive power.
While their can be no doubt that emancipation and citizenship for blacks and former slaves was a good thing. It was not Lincoln's goal in preserving the union.

The issue I want to point out primarily is "The Homestead Act" the Homestead Act, in it's essence, tore up every Treaty created by the Jackson Administration during the "Indian Removal Act". These treaties guaranteed sovereign territory west of the Mississippi river to the Indians formerly inhabiting the South Eastern United States. The treaties, while not wholly fair, did grant money, rights, legal protections, citizenship, and larger amounts of land than what was given up, to the Native Americans. And I'd like to say MOST left willingly (that is, with agreement to the treaty) albeit with heavy hearts. The criticism for these Acts, lies primarily in the short time frame given, and lack of proper federal assistance (rather federal prodding) in helping the Natives emigrate. So many died from exposure, disease, and lack of supplies from the journey.

The Homestead Act tore up those agreements, and made possible, the easier manipulation of the Indian protectorates, and the thievery and relocation of their land. Which in the long term, has caused more heartache and deaths than their initial removal (which prevented territorial wars from breaking out with american settlers, expanding in the South. [Whether it was right, is up for opinion, but the relocation likely protected the tribes from the onslaught of racial bigotry that was common in the Americans, and only to get more harsh in the coming decades with the Slavery debates]

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I don't fault Lincoln entirely for the effects of the Act, as he was assassinated before he could fully spell the effects of what it may have caused, of which some were becoming apparent, and seemingly affected him on some emotional level.

But any legislation, will always have effects that are perhaps good, or bad, in the long run or immediately.

But this is a good point to discuss when talking about the flaws of Lincoln's administration, and whether it was a good move, and how it should reflect on his presidency as a whole.