Question

how does the way that john stephens was killed support the idea the ku klux klan was a terrorist organization?

Answer 1

Because it was done that way to spread fear and send a message.
It wasn't simply murder, it was a statement.

Answer 2

John Stephens had his political life marked by encouraging blacks to engage in political activities. His posture and popularity among blacks was negatively seen by white democrats. He was therefore killed by the Ku Klux Klan in 1870 for being considered a state traitor, and his murder was a warning to other possible politicians who dared to fight in any way for the black cause.