Final answer:
Preston Brooks attacked Charles Sumner due to Sumner's abolitionist speech that condemned slavery and insulted a proslavery senator, triggering a violent defense of proslavery honor.
Step-by-step explanation:
Representative Preston Brooks attacked Senator Charles Sumner violently in the Senate chamber for his abolitionist view. This infamous incident occurred on May 22, 1856, and is known as "Bleeding Sumner," which was a consequence of Sumner's "Crime against Kansas Speech."
In this speech, Sumner had condemned the expansion of slavery into Kansas, characterizing it as a moral crime and the act of slavery itself as a harlot desired by proslavery politicians.
Brooks, enraged by the personal attacks made toward his cousin, Senator Andrew Butler, and the assault on proslavery views, took it upon himself to defend the honor of his family and the Southern stance on slavery. He felt Sumner was unworthy of a duel and instead opted to brutally beat him with a cane after the Senate had adjourned, nearly killing him.