Leyline of Sanctity stays in the sideboard here. It only gives us hexproof, and Bant Control's interaction (Swords to Plowshares, Leyline Binding, Solitude's exile trigger) targets creatures or permanents rather than us, so it would do nothing against their plan. Instead we bring in Thoughtseize to strip their key interaction before we go off. It takes any nonland card, such as Force of Will, Force of Negation, Swords to Plowshares or Solitude, which makes it much more flexible than Cabal Therapy, which needs a name guess against a deck with a wide range of interchangeable answers. Cabal Therapy's flashback also costs us a creature. Destroy the Evidence is too slow and narrow here. Thoughtseize costs us 2 life, which is a fine price against a controlling deck. Prioritize resolving our combo through their countermagic suite (Force of Will, Force of Negation, Spell Pierce), and use Thoughtseize early to see what they are holding and take the card that would stop us.