Bully social bane interacting multiplicatively with some defense cards

I received the social bane "Bully" (Lose 1 Defense on all cards that apply Defense) from Patrol Leader Gen and it reduced the effect of Bolstered Plating from "Gain 1 Defense per card in your hand" to "Gain 0 Defense per card in your hand", making it useless.  The description of bully gave me the impression that the intended interaction would be "Gain 1 Defense per card in your hand -1".  Also, I didn't specifically check, but I think it was having a similar effect on Defensive Surge by lowering it to 1 Defense per card played this turn.