The Ludwig von Mises Institute has repeatedly outlined how tyrannical Lincoln was. You might want to check who the current head of the Von Mises institute is.
All that may be true, but they point out that the Conf3deracy was Socalist, and tyrannical.
Anybody can call somebody a "tyrant" because the word is meaningless without context.
In this particular case, the context question is whether Lincoln was any more "tyrannical" than Jefferson Davis?
Every account I've read says that, relative to populations, Jefferson Davis: