fighting over nothing; making a mountain out of a molehill
Idiomatic expression derived from a classical Chinese story about a battle over a snail's horn, used to describe trivial disputes or much ado about nothing. Often used in literary or formal contexts.
Their argument is truly a fight over nothing.
Quarreling over such a small thing is what you call making a mountain out of a molehill.
A yojijukugo meaning 'exaggeration' or 'making a big deal out of nothing', but 蝸角の争い emphasizes the conflict itself rather than the act of exaggerating.
From a classical Chinese parable in the Zhuangzi where two states on a snail's horns fight a war, symbolizing the futility of trivial conflicts. The exact historical derivation is uncertain, but the expression is well-established in Japanese literary tradition.