Wasn't Andrew Johnson strongly in favor of punishing Confederate leaders? That would probably account for him criticizing Lincoln for being too soft.
Johnson was worried by the antebellum elite's continued control over the South and the presence of former Confederate leaders in Congress. He believed the rebellion needed to be punished and power shifted to small farmers and artisans. He did not, however, find any disagreement with the South on social issues and felt it within the South's rights to pass the black codes.
(He did later soften on the elite and granted mass pardons to former Confederates when it became obvious he would find very few allies in the North.)
On the other hand, Lincoln viewed the Southern aristocracy as less important and focused on emancipation. This earned him criticism from the Radical Republicans who viewed him as being too soft on the South. It was the desire for the Northern states that the South publicly accept its defeat and destroy any vestiges of Confederate loyalty in its entirety.
The Ten percent plan is the only official proposal regarding Reconstruction we have from Lincoln, although we can guess at what policies he would take from his speeches. His Second Inaugural Address, in particular, shows a man who wants to restore and rebuild the Union as soon as possible. It also shows a man who believes that slavery is an unmistakeable evil which must be expunged from the earth.
Nothing is going to discredit racism in that era. You might as well try to discredit eating beef, or hunting whales.
I agree here. Very few Northern states treated African Americans the same as whites before the law. Even widespread enfranchisement was controversial because many Northerners did not believe former slaves could make educated votes. Instead, Northerners focused on improving the quality of life. Political rights were a secondary concern.