“Lincoln sucked just as bad, or worse, than other presidents…” Wrong, wrong, wrong. Look at the three presidents preceding him — Millard Fillmore, Franklin Pierce, James Buchanan — who did such a sucky job of dealing with secession and slavery (namely, they pandered to the South).
“[He] bust his ass to keep the Union together so he wouldn’t be universally scorned.” Completely inaccurate.
As for Vallandigham, you’ll really ought to include the larger context.
The Copperheads were a northern antiwar faction of the Democratic Party that wanted to make peace with the Confederacy. Some Copperheads coordinated with the Confederacy. They were planning a secession of the Midwest. In southern Illinois, Copperheads organized the killing of Union soldiers. Clement Vallandigham received Confederate funding. He positioned the war as about freeing the blacks and enslaving whites.
So, it’s not that Vallandigham was some random dude who expressed some opinions and then got treated unfairly.