Hair-Splitting Meaning

(idiomatic) the act of finding exceedingly small differences which are probably neither important nor noticeable to most people.

Example: 2006, Ian Aitken, in The Guardian, Richard Clements Obituary
  Dick's Tribune poked endless fun at the hair-splitting sectarianism of the various Trotskyist groups jostling on the fringes of the Labour party at that time.