And when Korras made his identity apparent, let me repeat that no one even asked him to come back with them and help with the cure. This is a fellow human being, a fellow captive, and one with whom they stood a reasonable chance of convincing to help them. Isn't this exactly where years of Jedi training to detach oneself from his emotions would come into play?

The much larger picture here is one which Obi-Wan should have been aware of - uniting the enclaves to stand against the Malnosso. Instead, he isolated Luceti further.

While I understand that he was not in the best state of mind, the conversation could not have taken more than three real time minutes. Again, the request to help had not even been made before Obi-Wan chose to risk Korras' life and aid (what if they'd needed more than the man's body?) in order to shoot and abduct a man who was talking with them peaceably.

Again, I have to urge you to reconsider your characterization in this matter. The stakes are very high here. If you are determined that this is the most IC response he would have taken, of course that is your preference, but it is by all objective measurement an evil response. It was completely dictated by fear and impatience. And I hope to see the implications of him giving into such dark emotions in the future. After all, fear leads to anger, anger leads to hate.