In that, Loki was right. It wasn't a matter of "can't". Either way, it would amount to the same thing. "It wouldn't matter what I did, what must be will be." Exile was certainly in the cards, but not as Loki wished, or could even fathom. The seeress may not have given all the details, as volvas have a tendancy to do, but she gave enough.
Odin's word was law. Should he order everyone to stand down, most of them would. There were a few, though, like Skadhi, that he wondered if even his decree would halt. From what Odin could see, that woman was too full of hate and too unwilling to understand her father's part in his own demise, to listen to reason. And even if he managed to stall the inevitable, it would only be a temporary reprieve. There was no saying it wouldn't be worse should he try to interfere.
Why was he here? Odin knew, deep down, that it wasn't for Loki's sake. What would the Trickster gain by knowing the truth? Nothing. It was for himself, to attempt to ease his own conscience. "It may be that it will be a long time before we meet again, Loki. You will blame me for what will transpire, if only because you think I did nothing." And then it would all fall apart- the beginning of the end. If this was indeed the event the seeress spoke of, when next they met it would mean both their deaths.
"I could tell you to run, run far and run fast. I could tell them to leave you be. In the end, it will not matter. What must be will be. No one escapes their Wyrd."
Odin sighed again, knowing nothing he could say would make Loki understand. Well, there was one thing. It might not make understanding any easier, but it may help him to see that what Odin did, he did because he had to. In his relentless search for wisdom, he finally saw that knowing wasn't always better.
"Sometimes even my hands are tied, and that which I would not will I must accept. I am going to tell you something I have told no one, not even Frigg. Something I can only hope you will keep to yourself. I share it now, both as proof of my sincerity, and in the hopes you can see you are not the only one that must suffer what the Nornir have decided."