I know I would rather the certainty of safety, food, and dragon hide than the slim possibility that it is a creature of reason and loyalty. I do not mean to imply that alliances and diplomacy are worthless; however in our current situation I believe that we must think of ourselves first. Particularly since the creature has already taken lives.
We would not waste time trying to reason with an encroaching tribe who uprooted and murdered Grounders. We should not do it with a dragon.