The hemming and hawing should not happen, you're right.
The problem here isn't on the player side. The GM is cheating. Accidentally, but still cheating.
GM Cheating in Dungeon World
The GM cheats in Dungeon World when they speak without following their Agenda, Principles, and Moves.
There is no GM move called "make an arbitrary decision." There's also no GM move called "have a freeform social interaction." If the GM is following the rules, this kind of stall should not happen.
This is why the GM has rules, to prevent situations like this one, among other situations that qualify as failure modes to avoid.
Responding to a polite request, as the GM
The player's job is done: they've had their PC ask politely. There is no error on the player side of the equation and nothing to fix, no other moves to try to bend to fit the goal.
Since the “everyone looks to you to find out what happens” trigger matches, it's now the GM’s turn to make an appropriate move, instead of falling into “time for unstructured social exchange improvisation!” habits that they have brought with them from some other game.
(Recall too that moves aren't optional when triggered: when that trigger happens, a move must be made; this is equally true for GM moves as for player moves. The GM's turns has been triggered and making a GM move is now demanded by the rules.)
There are several moves that the GM could make. All of them, if executed with the Agenda and Principles in mind, should immediately add something new and interesting for the players to engage with, not just chit-chat.
The trick is to pick one, and then do a quick mental Mad Libs to fill in the blanks that the move demands. Let's assume the PC has politely asked for that magic sword:
Reveal an unwelcome truth:
“Sure, you can have my sword! It's cursed. If you can take it from me, I'd be more than happy.”
Show signs of an approaching threat:
“What kind of a person asks for a warrior's sword?” the bandit chief growls. She's obviously really insulted just by the question. It looks like she's thinking of giving it to you, point first, if you can't mend the situation. What do you do?
“This old thing? Uh, sure! Here!” he says breathlessly. He almost pushes it into your hands, and then runs off. It's a very fine sword, clearly magical and worth a lot. As you look up from admiring it, you notice a posse of civilians with torches and pitchforks lead by three members of the city watch running in your direction. They're shouting something that sounds awfully like “Thief!” What do you do?
Turn their move back on them
Possibly the simplest and most straightforward move to make: ask them to tell you why in the world their polite request makes any sense! If they're asking in the first place, they might see a good reason that you're not seeing.
— Hm, you're just asking? Okay, well why do you think they would just give it to you?
— Because the village owes us their lives and souls, and we're heroes. He'll probably gift it to us.
— Huh! Well at any other time I'd laugh and so would he, but yeah, considering what you just did? Yeah, they gift you the sword. They even make a big ceremony of it. You're big damn heroes!
Give an opportunity that fits a class’ abilities
Have you got a thief in the party? Well...
He laughs that off. “Just give you my sword?! You must be soft in the head.” He turns and walks off, shaking his head and laughing. But you get a good look at his sword belt from behind and notice it's worn... given the right chance, you could probably cut it quick. Want to tail him?
Tell them the requirements or consequences and ask
This is a staple of responses to polite requests. This prompts the GM to set a price, and ask.
She says sure, she'll give you the sword. But only if you defeat her in single combat. She seems pretty confident too. What do you do?
“Sure. What's it worth to you? How about... that emerald necklace and arranging an audience with the Unmasked Lord for me? No? Well... let me know if you reconsider.”
“Hm, alright. Do you have three hundred crowns?”
“I tire of the burden. It is yours if you want it. But beware: the sword has a way of making heroes out of its bearers, whether they mean to be or not. Take it only if you are willing to shoulder that burden.” He holds the sword out, hilt first. What do you do?
The point is that the PC “just” asking is just the beginning, and there is nothing that says “just asking” is suddenly set in stone as the price at stake. The GM's job is to play to find out what happens, and to do that you pick a GM move, fill out its details, and play out that response. The result will almost certainly establish that there is a price beyond politely asking, either of in-game goods to exchange or in narrative branches the players must tackle. Rather than deciding, you add something interesting to the situation and then see what the players do.
So clean up the GM's side of these meandering social improv interludes, and you won't see stalls anymore! The GM might even be surprised by the things they spontaneously add to the game, faced with such circumstances. This is where Dungeon World shines: turning mundane, boring bits of play into pivotal moments, because the rules demand never doing something boring and stale.