First, Ron is going through a lot of emotions, the most powerful one being jealousy. As anyone could see that read the book, Ron felt this jealousy for a lot of the book. First with Harry getting into the tournament(Harry was getting attention that Ron never got and wanted as his mother was nice to him, but he was ignored by people at his school and his mother never pampered him like she did Harry) and then with Victor Krum basically stealing the girl he liked (or didn't know he liked till then).
The Yule Ball argument was a progression that came on slowly and simmered until it burst on that night:
Another note is that he is also learning of his feeling of for Hermione, but like all the books he doesn't know how to go about them.
Ron wanted to go to the ball someone (Hermione being one candidate), but he waited till a short time or so before the Yule Ball to even approach the idea of taking her. And then when she turned him down, he thought this as another slight, not that someone else would have wanted to take her as well. He thinks that she will be waiting for him, but is not and that irks him.
From pg.400 Chapter 22 "The unexpected Task"
"......But Ron was staring at Hermione as though suddenly seeing her
in a whole new light.
"Hermione, Neville's right- you are a girl......."
"Oh well spotted" she replied acidly.
"Well- you can come with one of us!"
"No, I can't," snapped Hermione.
"Oh come on," he said impatiently, "we need partners, we're going to
look really stupid if we haven't got any, everyone else
has............."
"I can't come with you," said Hermione, now blushing, "because I'm
already going with someone."
"No you're not!" said Ron. "You just said that to get rid of
Neville!"
"Oh did I?" said Hermione, and her eyes flashing dangerously" Just
because it's taken you three years to notice, Ron doesn't mean no one
else has spotted I am girl!"
Then slightly later after she leaves.
"She's lying," said Ron flatly, watching her go.
"She's not," said Ginny quietly.
"Who is it then?" said Ron sharply.
I'm not telling you its her business," said Ginny.
"Right," said Ron, who looked extremely put out....................."
From pg. 399 Chapter 22 of Goblet of Fire "The Unexpected Task", Ron said this:
"......................but she told him she was already going with someone. Ha! As if! She didn't want to with Neville...... I mean who would?"
From that quote you could see that he was feeling superior and felt that she would always be there, because she wouldn't get with the dregs(in his opinion or anyone higher up wouldn't want her, he probably still sees her as the bookish nerd with the bushy hair and buck teeth). We know from this same book and chapter that he has a certain "idea" of what beauty is. He probably doesn't understand his feelings for her yet either, as he is either 14 or 15, possibly 13(very young and going through puberty).
And on pg.394 Ron talks more about his choices in partners which insults woman and offends Hermione.
Once he realized who she went with he probably felt a even more slight and as she went with Victor Krum(Quiditch player and Champion for his school), but she didn't go with him. He was probably feeling inadequate.
Chapter 23 The Yule Ball
"Ron was watching Hermione pass with narrowed eyes....."
Then on Chapter 23 The Yule Ball pg. 420-421
Ron has a beginning argument with Hermione and explains his displeasure as due to the fact that Victor is from Durmstrang and that she is supposed to be helping Harry. But he himself had no problem with ignoring Harry and treating him poorly for the first challenge, so that is probably not it. Also, he destroys his Victor Krum merchandise after that argument, when he of the 3 friends was before the biggest supporter of Victor Krum.
And then that brings me back to your quote.
Hermione and Harry knew that his anger was at least jealousy or a blooming love whichever. That is why he
"................mouthed soundlessly like a goldfish out of
water.........................." and he "..............sputtered,
looking thunderstruck, "well- that just proves- completely missed the
point-". Chapter 23 The Yule Ball, pg. 432.
From that quote he is probably realizing what they are saying is true and is embarrassed.
But Harry and Hermione both knew that Ron liked Hermione and the fact that he only realized it till then, probably because he was too busy looking at Veela and playing. He vented his anger as not liking the fact she was fraternizing with enemy, but it was really jealousy.
Also, other people went out with others from other schools, but he only chose to zero in on Hermione. Because it was personal.
Another thought is that he thought Krum was just using her to get answers, like he does during school. Maybe he was telling the truth during the ball and he was just trying to look after her best interests.
