Keitt was censured by the House in 1856 for aiding Rep. Preston Brooks in his Caning of Charles Sumner. Brooks had considered challenging Sumner to a duel after Sumner's anti-slavery The Crime Against Kansas speech, which Brooks interpreted as an insult to his cousin, Senator Andrew Butler. After consulting with Keitt and deciding that Sumner was no gentleman, and therefore not worthy of a duel, Brooks resolved to beat Sumner with a cane instead. With Keitt and Virginia Representative Henry A. Edmundson on hand to assist, on May 22, 1856, Brooks entered the Senate chamber and began beating the defenseless Sumner with his gold-headed cane, while Edmundson and Keitt prevented others from stopping Brooks or aiding Sumner. Keitt drew a pistol from his belt and brandished his own cane, holding off the horror-struck senators who tried to assist Sumner, loudly announcing "Let them be!" In July, the House censured Keitt for his part in the attack. He resigned in order to create a vacancy that would be filled by special election, thus giving his constituents the opportunity to ratify or condemn his conduct. They supported Keitt's actions, overwhelmingly returning him to Congress in the August special election. He served until December 1860, when South Carolina seceded from the Union.
Later career
On February 5, 1858, Keitt started a massive brawl on the House floor during a tense late-night debate. Keitt, offended by Pennsylvania Congressman Galusha A. Grow, a Republican, having stepped over to the Democratic side of the House chamber, dismissively demanded that Grow sit down, calling him a "black Republican puppy". Grow responded by telling Keitt that "No negro-driver shall crack his whip over me." Keitt became enraged and went for Grow's throat, shouting that he would "choke for that". A large brawl involving approximately 50 representatives erupted on the House floor, ending only when a missed punch from Rep. Cadwallader Washburn of Wisconsin upended the hairpiece of Rep. William Barksdale of Mississippi. The embarrassed Barksdale accidentally replaced the wig backwards, causing both sides to erupt in spontaneous laughter. Perhaps Keitt's most famous quotation best summarized his political views and dominant agenda. In 1860, Congressman Keitt said, "The anti-slavery party contends that slavery is wrong in itself, and the government is a consolidated national democracy. We of the South contend that slavery is right, and that this is a confederate republic of sovereign states." After South Carolina's secession Keitt served as a delegate to the Provisional Confederate Congress from 1861 to 1862.
Keitt later joined the Confederate States Army, and attained the rank of colonel as commander of the 20th South Carolina Volunteer Infantry Regiment. He later commanded Kershaw's Brigade, succeeding to this position after Kershaw advanced to command of a division. Mortally wounded at the Battle of Cold Harbor on June 1, 1864, Keitt died the next day near Richmond, Virginia. He is buried at West End Cemetery in St. Matthews, South Carolina.