Okay, let’s talk about this scene for a minute. We already know that it’s foreshadowing Thorin’s downfall, but can we consider for a minute that it’s not foreshadowing the things that it’s meant to be foreshadowing?
Gandalf accuses Thorin of holding on to the past - how do we learn how to react to future difficulties except by using past situations as an example? The last time Thorin went to the Elves for help (remember the flashback? Remember our desperate dwarf prince screaming for help at an indifferent-seeming Thranduil? Good because a lot of people don’t), none came. This was about something huge, there were injured terrified refugees coming out of that mountain with nothing. And Thranduil didn’t lift a finger. Didn’t even tell them where to find clean drinking water.
Sure, Elrond and Thranduil are completely different people, but Thorin doesn’t know that. At best, he thinks they’ll be turned away, at worst he thinks that Elrond will actively work against him to stop the quest (he’s not wrong about that last part, even if it was Saruman who wanted to call a halt).
Gandalf accuses Thorin of being proud, but is that pride? Once bitten, twice shy after all, can Gandalf honestly expect that Thorin is going to forget or lay aside all his misgivings (which are valid) just because he said so? Gandalf never tries very hard to convince Thorin that Elrond will be helpful, he just expects Thorin to take him at his word.
To me, this is part of a larger pattern in this film and in the book of other races and beings not taking the dwarves seriously. Everyone is patronizing toward them (except for Elrond, he’s pretty great, but again Thorin doesn’t know that). Gandalf gives orders and expects obedience (would he talk to Aragorn this way? Theoden? Even Bilbo?), Bard acts as if he knows more about the sacking of Erebor and Dale than Thorin does, (“Have you forgotten what is in that mountain?” Um, no, Bard, considering the fact that he lived through it.), Thranduil locks the dwarves up because they won’t give him gemstones that he’s demanding - not in exchange for “help” as he says, but to secure their release after they were arrested without cause. And then, in the end, Gandalf, Bard, and Thranduil, stand against Thorin, using a stolen relic of his people as a bargaining chip. A relic they had no right to, they threaten him with force and steal from him and all the whole we’re hit over the head with the idea that Thorin brought this on himself. Why? Because he’s a proud, stubborn dwarf. And we’re supposed to accept that explanation, having allegedly seen evidence of it here.
Yeah, this foreshadows the Arkenstone debacle. This foreshadows Men, and Elves, and Hobbits, and wizards not giving a fuck about the dwarves’ rights to their own property. It’s a pretty beautiful metaphor for the dwarves’ entire existence, they only exist because of the indulgence of Illuvatar and by the indulgence of Illuvatar’s children they are permitted to keep their kingdoms. It’s all well and good when they’re mining mithril for the Elves or trading with Men, but the second a dwarf does something they don’t like, or they encounter a problem that would put the lives of other races at risk, all of a sudden they’re greedy, they’re prideful, no one wants anything to do with them.
Just listen to Gandalf here. “I did not give you that map and key for you to hold on to the past.” That key was fashioned by dwarven hands to open a door carved by dwarven masons to enter a dwarven kingdom. That map was created by dwarves to enter that same kingdom. It was retained by a dwarven king to give to his son - yet once Gandalf has it, it’s suddenly his map. Thorin has no right to it except by Gandalf’s deigning to hand it over. Who’s proud, again?
Yeah, someone is very wrong in this scene. But it’s not Thorin.
And no one ever mentions the fact that Gandalf has had that map and key for basically a century and is only now giving them to Thorin. I believe he says somewhere that the Dwarf he got them from was crazy and near death, but honestly! It’s a map of the goddamned Lonely Mountain with an arrow pointing to a hidden door. How much thought does it take to come up with the fact that it should go to Thorin and probably the crazy, dying Dwarf was Thráin? Way to take a century to confirm his death to his own son. And then act like you’re doing him a huge favor by giving him something that should have been his in the first place. I’m normally very fond of Gandalf, but not when I think of him in relation to Dwarves.
Also, for all that Elrond reads the map for him, he also did the condescending “there are some who would not deem that wise” in the way that parents might tell children that going sky diving might be dangerous. Because Elves always know best, right?