Google translates "couper les cheveux en quatre" as "niggle" OR "splitting hairs" meaning:
'Niggle'
nig·gle
ˈniɡəl/
verb
1.
cause slight but persistent annoyance, discomfort, or anxiety.
"a suspicion niggled at the back of her mind"
synonyms: irritate, annoy, bother, provoke, exasperate, upset, gall, irk, rankle with;
More
find fault with (someone) in a petty way.
"colleagues say he loved to niggle and criticize people"
synonyms: complain, quibble, nitpick, fuss, carp, cavil, grumble, gripe, grouse, moan
"he niggles about the prices"
noun
noun: niggle; plural noun: niggles
1.
a trifling complaint, dispute, or criticism.
synonyms: quibble, trivial complaint, criticism, grumble, grouse, cavil;
OR
split hairs definition. To argue about an inconsequential and trivial aspect of an issue: “When you are accused of being forty-five minutes late for an appointment, you are splitting hairs to say that you were really only forty minutes late.”
just sayin'