ODIN: With the last great war ended, we withdrew from the other worlds and returned home at the Realm Eternal, Asgard. And here we remain as the beacon of hope, shining out across the stars. And though we have fallen into man's myths and legends, it was Asgard and its warriors that brought peace to the universe. But the day will come, when one of you will have to defend that peace.
Odin's very clear from the beginning what's expected of Thor and Loki: keep this place safe, because war and horror really stink. They can't say that they don't know how to behave properly.
THOR: When I am king, I'll hunt the monsters down and slay them all! Just as you did, Father!
ODIN: A wise king never seeks out war. But he must always be ready for it.
Again, Thor can't claim he doesn't know how to do the right thing. Odin spells it all out for him.
HEIMDALL: Be warned, I shall uphold my sacred oath to protect this realm as its gatekeeper. If your return threatens the safety of Asgard, my gate will remain shut and you will be left to perish on the cold waste of Jotunheim.
Heimdall, at least, hasn't taken his eye off the ball. Here he spells out his personal ethics—duty before everything—and has the courtesy to let the others know what that means for them. Nice of him to do that.
THOR: The Jotuns must learn to fear me just as they fear you.
ODIN: That's pride and vanity talking, not leadership!
Again with the rules spelled out. Odin correctly points out that ending the threat of the frost giants means more than just bashing them on the head. Thor needs to learn that before he can rule.
LOKI: Why? You were knee-deep in Jotun blood. Why would you take me?
ODIN: You were an innocent child.
LOKI: No. You took me for a purpose. What was it? Tell me!
ODIN: I thought we could unite our kingdoms one day. Bring about an alliance, bring about permanent peace... through you.
Loki really doesn't understand why Odin would do what he did. The thought of some greater good being served by taking a baby from a battlefield is truly beyond him. That, at the end of the day, is why he's the bad guy.
THOR: Once I have Mjolnir, I will return the items they stole from you.
Another ethical misstep here, even though Thor is ultimately trying to do the right thing. He sees getting his power back as the main goal, with Jane's stolen notes as an afterthought.
LOKI: I will conceal you, and a handful of your soldiers, lead you into Odin's chambers and you can slay him where he lies.
LAUFEY: Why not kill him yourself?
LOKI: I suspect that the Asgardians would not take kindly to a king who had murdered his predecessor.
This is typical bad guy stuff, and we can't say we're surprised. But sneaky cuts both ways, and in this case, it's more compacted than that. Loki isn't trying to betray Odin: he's setting up Laufey, as a way of weakening Asgard's enemies. In his own sick way, he's doing the right thing: the thing Thor originally wanted to do. And if Thor hadn't caught wise at just the right time, he likely would have made it happen…
HEIMDALL: You would defy the commands of Loki, our king? Break every oath you have taken as warriors, and commit treason to bring Thor back?
Heimdall, stickler for the rules, is able to eel around his rigid ethics system in order to do the right thing. It's interesting the ways he sticks to the letter of his duty while ignoring the spirit…suggesting that he still won't break his word to help Thor. He's just found a way around it.
ERIK: I still don't think you're the god of thunder. But you ought to be.
Erik's first admission that Thor might actually be a better guy than he first thought is important, since it happens at the same time as Thor's moral awakening. It suggests, very subtly, that Thor always had the capacity to be a hero in him. He just needed a swift kick in the rear to bring it up.
FRIGGA: There's always a purpose to everything your father does.
Thor bashes without thinking. Odin bashes only after his son is completely out of control…and then only as a way of showing him the error of his ways. That's the difference between good judgment and a temper tantrum.