Unless you have a personnel who has 2 Diplomacy or a personnel who has 2 Leadership, your opponent chooses a Diplomacy or Leadership personnel to be stopped. If your opponent cannot, all your personnel are stopped and this dilemma returns to its owner's dilemma pile.
"You swear well, Picard. You must have Klingon blood in your veins."
Image courtesy of trekcc.org
No copyright infringement intended