He could be again, for the right cause. The only cause that matters now is freedom at any cost. He's already made his peace with the possibility of dead ends. It's still preferable to having his mind slowly stripped down until he somehow becomes content to live indefinitely in a place like this. Taking the Captain down with him is undoubtedly the only way to be sure this ends for good.

"I'm no stranger to suffering. I don't cower in the face of it. I'll fight, with or without you. I never intended to do anything else."