Sometimes it do backfire though, for example imperial comissar Yarrick fought successfully against some of the biggest orkish invasions and improved this by conscious propaganda effort aimed at both his soldiers and orks, and orks did believed in him as the main boss of humans and thus their own belief empowered him. Not that they seen it as backfiring, in the contrary the bigger and harder the fight the better, in fact orks are routinely disappointed when the fight is too easy, they prefer hard massacres with huge losses on both sides (which might partially explain why 40k setting is so full of pyrrhic victories in general).
Sometimes it do backfire though, for example imperial comissar Yarrick fought successfully against some of the biggest orkish invasions and improved this by conscious propaganda effort aimed at both his soldiers and orks, and orks did believed in him as the main boss of humans and thus their own belief empowered him. Not that they seen it as backfiring, in the contrary the bigger and harder the fight the better, in fact orks are routinely disappointed when the fight is too easy, they prefer hard massacres with huge losses on both sides (which might partially explain why 40k setting is so full of pyrrhic victories in general).