Dimir Midrange is loaded with countermagic (Counterspell, Force of Negation, Spell Snare, Subtlety) and discard (Thoughtseize), so proactively stripping their interaction with our own Thoughtseize before deploying our combo pieces is critical. Surgical Extraction is useful to exile a copy of Orcish Bowmasters or Psychic Frog from their deck once one hits the graveyard, reducing the density of their best threats. Their deck has very little targeted removal for our small creatures beyond Fatal Push, so our board development plan is largely intact. Cut Haywire Mite and Sylvan Safekeeper since they have almost no artifacts/enchantments to attack and their removal suite doesn't heavily threaten single creatures worth protecting.