Final answer:
Charles Sumner's speech criticizing slavery and insulting Senator Andrew Butler, with personal and provocative language, led to Sumner being attacked by Butler’s cousin, Preston Brooks, on the Senate floor.
Step-by-step explanation:
Charles Sumner provoked the Sumner-Brooks incident by delivering a controversial speech that criticized slavery and insulted Senator Andrew Butler. On May 19, 1856, during his "Crime against Kansas" speech, Sumner condemned the Kansas-Nebraska Act and the spread of slavery to new territories, referring to slavery as a "harlot." He specifically targeted Butler, accusing him of a personal relationship with slavery akin to a man’s lust for a prostitute, an accusation he ardently defended as a member and byproduct of the slave-owning South.
These incendiary remarks ultimately led to Butler's cousin, Preston Brooks, attacking Sumner on the Senate floor with a cane on May 22, 1856. Brooks justified his violent response by claiming Sumner had libeled South Carolina and his relative. The attack left Sumner seriously injured and became a polarizing event, highlighting the escalating tensions between anti-slavery and pro-slavery factions in the United States.