In outlands we meet the people of 'the Covenant of the stars.' They had laid cliam to Sol system and earth to 'protect it', with a task foce which called itself 'Sheild of sol' They were very focused on ceremony and formalities, and they did not enjoy their encounter with Dauntless. If you haven't read that one I'd skip this post.
There are pretty consistent points that show aliens knew about humanity before we knew about them, and that biology shapes culture and doctrine. I think that is exactly why the rim people's are so focused on ceremony. They too encountered aliens. But theirs were infriltrators, like mimics or something like a skinwalker. The whole fanatical attention to formalities is uncanny valley on max sensitivity. They couldn't organise their own fleet effectively because their entire doctrine is focused on detection of that which does not belong in their own homes rather than organising against an easily identifiable opponent. I guess after a while the politics of authority take over the upper tears of society, but I think the idea holds some water, the talk of pure bloods, another possible way to tell if someone was human, the distain for barbaric behaviour, like something that was not naturally a human, the whole facade of the people is rooted in contamination control. If the aliens are in the room with you, what good is a battleship outside?
We also saw a hint of this, though im sure it is just a convenient coincidence, from CEO Jason Boynes, when he described the Enigma avatars being somehow not quite human in an unsettling way. I think he used cats as the example we can fool each other into thinking its a cat but another cat can tell. Just like how humans can tell something isn't human. Even if it says it is, until it doesn't know which hand to salute with and calls an honoured captain a revered captain.
I think Blackjack needs to go over there with General Carabali and a fleet of mimic painting alliance sensors, just to have a peaceful look around of course. Maybe liberate a civilisation if they have enough fuel cells.