Grixis Affinity is built entirely around artifacts (Myr Enforcer, Refurbished Familiar, Ichor Wellspring, artifact lands), making Steel Sabotage a strong include to counter a key artifact spell or bounce a problematic Myr Enforcer before it threatens lethal with Galvanic Blast. Blue Elemental Blast and Hydroblast are not dead here: they can counter or destroy the opponent's red cards, namely Galvanic Blast, Krark-Clan Shaman and Makeshift Munitions. Those targets are few, though, so they stay in the sideboard in this plan. Deem Inferior is too slow here since the opponent's affinity threats come down quickly and cheaply, so proactive artifact disruption is more valuable than tucking one permanent. Lean on Counterspell and Dispel to stop Galvanic Blast from reaching your face or a key creature.