I get this concept on the level of "we don't like when our army is stabbed with pointy swords even though our army is itself equipped with the very same pointy

I get this concept on the level of "we don't like when our army is stabbed with pointy swords even though our army is itself equipped with the very same pointy swords" but the word 'shady' is funny to me in this context. I mean if that's the analogy then it's like if you are in a melee and you look at your comrade in arms next to you getting stabbed by the enemy and you describe it as 'kind of sus'.