It doesn’t matter about the orders, Luffy would literally be letting the only person to kill a nakama/family member walk away free.
Luffy has to fight Blackbeard, and he has to fight Akainu. Just storywise, ignoring feats, if either of those battle doesn’t happen it’s drop worthy.
If Cracker killed someone Luffy cared, its not going to be about Cracker, it's going to be about Big mom, because Big mom orchestrated the whole thing, Cracker was just following orders. Just like Bellamy was following orders, Luffy wasn't mad at Bellamy, he was mad at Doflamingo.
Akainu is the same.
Sengoku was the leader and he gave the order.
Gorousei or Kong gave the order to Sengoku.
Imu gave the order to Gorousei.
Akainu is an irrelevant pawn in the big picture.
Blackbeard orchestrated his whole game plan and his actions, he isn't a pawn in someone's game.
Which is why Imu goes nuts in the flower room and cuts Blackbeard's wanted posters alongside with mc Luffy, which is why Aokiji decides to be a pawn for Blackbeard, instead of being an Admiral.
Akainu is not important like that, not even close. If they tell Akainu stfu and not kill someone, he can't kill anyone or can't do shit, he is a pawn.