What does "defend" mean in "defend your rule"? Isn't "defend" used to attacking situation?
In this case, "rule" is used to mean "position" or "authority." The speaker has used this expression to tell the debate teacher that he needs to defend (protect) his position or authority as the debate teacher. "Defend" can also be used in situations not involving war or combat. For example, this context involves an element of competition, so "defend" can also be used here as well. Ex: Our school will defend our title as national champions. Ex: The soldiers were exhausted and injured, so they weren't able to defend the base against the enemy.