"She’s the antidote Eric, she can heal you. This is not about capture and kill anymore."
#Eric seems very agitated
I would guess that his drive for revenge has been obstructed with the knowledge that Sarah’s blood is now the cure. He wants to kill her. It’s the primary reason why he’s not lying in France dying. Now she’s the cure and if he kills her, does he have to worry that he affects the cure for all infected vamps? It seems like a no brainer, but, as we’ve seen before (writers?!), Eric can be very driven by revenge. My guess is he knows that he can’t kill her, but doesn’t want to accept it and that’s where the agitation comes in.