To Dedue, Ari seems to be a Faerghan knight. She talks of obeying orders and taking out hazards and it infuriates him. She would not know what actions that sort of language excused.

“Hazard?” he growls. “That is what this is to you? A hazard in your way?” He lifts the axe back up. “The lives here do not matter. All that matters are who gives you your orders,” he spits.