How did the beating of Charles Sumner represent the "breakdown of reasoned discourse" in the lead up to the Civil War?

Charles Sumner, a US Congressman from Massachusetts, gave a very passionate speech about the evils of slavery and those who support it. In response, Preston Brooks (another US Congressman) physically assaulted Sumner because of the way he spoke about southerners and the institution of slavery. Sumner suffered severe head injuries that would affect him for his entire life.

This violent outbreak showed that their was too much emotion involved in the issue of slavery to discuss it in a mature manner. Along with this, it showed that slavery was a cause that would eventually lead to violence between Southerners and Northerners.