Why did they call Abraham Lincoln a tyrant

Abraham Lincoln was seen as a dictator because he did not lead the country from within the confinement of presidential power within the written constitution. He repeatedly disregarded the constitution and had ruled America instead of leading. Lincoln violated separation of powers and made himself a dictator, which is why many say that (and so it seems that) he did not really have presidency. This is why Abraham Lincoln was labeled as a tyrant, due to his dictating ways.