Hannibal's response... was strangely unnerving, but Watson couldn't really put his finger on why. It was so matter-of-fact, but at the same time... he wasn't actually saying anything that he found unacceptable. And then, John was used to Sherlock. He was used to the seemingly emotionally distant state. Will crying save their lives? He understood, even if it seemed unusual.
After a moment, John nodded, and gave him a bit of a smile. "All right, then. We're glad to have your assistance, doctor."