My perspective of class threads (discussions) is to ensure the student has addressed the main topic, and then begin to challenge what they think they know or their opinions. I give them additional information to consider, see if they are willing to change their minds or stick to your views. If they choose to maintain their viewpoints, I try again, altering the facts slightly to se if the student is now willing to change their minds when a reasonable person would make adjustments in their viewpoints.
