Legally, there would be no basis for a suit in such a situation. You have significant issues with duty, breach and causation in your hypothetical. As stupid, asinine, and ludicrous as these decisions are, they are business decisions. The marketplace should punish these poor decisions. However, that will require gun owners and conservatives to put our money where our mouth is. Idle threats to sue when no basis would exist won’t change the minds of these corporate demons.
Tell that to the cake baker who said he would not bake a cake. Trust me they are going to get sued and for good reason.