Was Stanton a murder target?

[RJNorton]

John, on p. 364 you write:

"Arnold. Arnold was one of the ignorant ones. He and O'Laughlen were a sideshow compared to Surratt, Powell, Herold, and Atzerodt. When it became clear to Booth that the Baltimore duo were not killers, there was no way he was going to tell them what was really going on."

Knowing O'Laughlen was not a killer and was not to be told what was really going on, why did Booth want O'Laughlen to come to Washington on the 13th?