Why did the Elvenking set aside his anger at Thorin and decide that he would not begin a war for gold?

In Chapter 17 of The Hobbit, Thorin is acting quite stubborn about giving up any of the dragon's horde. As he says, "My mind does not change with the rising and setting of a few suns." Things get quite tense when Dain arrives with a dwarven army. The men and elves are between them and the entrance to the Lonely Mountain, and a fight looks inevitable. However, the Elvenking steps in and proclaims, "Let us hope still for something that will bring reconciliation." Clearly, he would like to avoid a battle.
Why the Elvenking was looking for a diplomatic resolution instead of a violent confrontation has to do with the nature of the elves. Throughout Tolkien, the elves only go to war once all other avenues have been exhausted. They see themselves as apart from the strife of dwarves and men. They also value their long lives and are not as quick to throw it away, as shorter-lived folk often are. We see their reluctance to fight in their absence from the Battle of Helm's Deep and their smaller-than-expected contribution at the Battle for Minas Tirith in the Lord of the Rings trilogy. So it is not surprising that, despite his ill feelings toward the dwarves, the Elvenking is not eager to engage in a pitched battle if it can be avoided. Of course, once the goblin army shows up, a fight is unavoidable and the elves join forces with the dwarves and men to fight together in the Battle of the Five Armies.