Sic semper tyrannis means “thus always to tyrants.”Why did Booth shout this about Lincoln?

Booth supported the Confederacy and regarded Lincoln’s effort to preserve the Union by defeating it as tyranny. By shouting “Sic semper tyrannis,” meaning “thus always to tyrants,” he was expressing his belief that Lincoln was a tyrant and that the Confederacy had a right to secede. The other choices do not fit Booth’s motive.

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