Warning: the following article contains spoilers for 86 Eighty-Six Episodes 18 "The Truth Is," now streaming on Crunchyroll.
The most confusing and frustrating thing about the ongoing story arc in 86 Eighty-Six is how Shin and his friends are viewed by most of the Giad Federacy's military. It makes no sense whatsoever and contradicts the Federacy's insistence that they're not like the Republic. It's true that in some ways the Republic is worse for their treatment of the Eighty-Six, but in other horrible ways, they're exactly the same.
The mission to destroy the Morpho, the newest and most dangerous type of Legion yet, officially commences in the latest episode. It's safe to say everyone is aware of what this mission really is. Its aim is not only to destroy the Morpho but to send Shin and his friends to their deaths. It wasn't clear in the previous episode what Ernst thinks about this mission, but his feelings are revealed in The Truth Is.
Ernst asks one of his officers directly if this mission is an attempt at a "disinfection." He points out that back when they had just taken Shin and the others in, some officers (including the one he's speaking to) said that it would've been better to eliminate the Eighty-Six for the safety of the Federacy. The officer denied what Ernst was implying but went on to say that they aren't poor, pitiful children but monsters created by the madness of the battlefield.
It's a mystery why the Giad military with the exception of Ernst and the Nordlicht Squadron which the Eighty-Six are members of, refuse to accept these teenagers. There is no real reason for the Federacy officers to be thinking of them as monsters who are harmful to their country. Shin and his friends haven't done a single thing wrong the entire time they've been citizens of the Federacy. They haven't gotten into any issues with anyone and they've done their part as soldiers.
The Giad officers believe that the Eighty-Six should be eliminated for reasons that only exist in their minds. Ernst is aware of this and is very much against it, but he's unfortunately unable to do anything about it. The Eighty-Six insist on going on the mission due to their ideals and pride, so even if Ernst could do something, it wouldn't matter anyway. He does the next best thing by telling them that their highest priority mission is to survive and return so they can fight till the end of the war.
Ernst proves that he genuinely cares for his adopted kids and that his ideals of what the Federacy should be are genuine, even if the rest of the militaries' are not. He declares to himself that Shin and his friends must come back alive no matter what, or he'll destroy the world. Interestingly, this isn't the first time Ernst has expressed his feeling that there's no point to humanity if they're unable to accept these kids. He explicitly said in Episode 12 that humanity would be better off dead if they can't survive except by killing children because they're strange.
It's clear now that Ernst means what he says. If the Eighty-Six ends up dying on this mission, in which case the other Federacy officers would surely rejoice, it's unlikely that he'll just accept it and move on. He genuinely wants the Federacy to be different from the Republic, and right now it barely is. He would rather see the world burn than accept that his own country would kill innocent teenagers for no good reason. Of course, even if they survive, that won't change the fact that they were sent to die. So, hopefully, Ernst intends to address this issue directly either way.