Their argument is just a tempest in a teapot.
tempest in a teapot
idiomA major fuss over a trivial matter.
Origin
first recorded 19th c.Attested since 1838.
The office staff spent hours debating the color of the new napkins, which was clearly a tempest in a teapot.
While the media treated the minor disagreement as a national crisis, the seasoned diplomat dismissed the entire affair as a tempest in a teapot.