The thing about that scene that I'm surprised so many people are not mentioning, is not that Sasha's dad threw her under the bus. It's that he did it for the walking shitstain that is Gabi. She'd proven herself to that point to be an irredeemable piece of shit that constantly instigated conflict and ran right into harm's way and yet just wouldn't die. Isayama makes you despise her more and more with every scene, wishing for her to just die, then finally creates a situation where she just might get what she deserves, only to blueball you by having Sasha's father blame her for dying.
It's the combination of all of this that makes that scene so distasteful imo. Think about it. If it was just Falco in that scene and Sasha's dad forgave him, would you hate it as much? Isayama completely botched the most basic of story arc: the redemption arc. He can't seem to do anything right beyond setting up the story.
Real talk, this is also it.
Gabi sucks. She really sucks. Say what you want about Levi, or hell, even Eren, they have moments where they're at least kinda cool, and likable, at least in the beginning of the series. The closest Gabi ever gets to that is when she no-scopes Eren's head, and even then, it's more of a giant WTF moment than anything.
Compare, and contrast Gabi, and Sasha for a moment. Sasha is kind, funny, has a unique skill with her archery, and her backstory is one that's actually pretty noble because she joins the military, risking her very life, just to make her parents proud. She's arguably one the most relatable, and realistic characters in the series. She also didn't hog the spotlight either.
Gabi, on the other hand, is bratty, bitchy, smug, racist, blatantly mary-sueish, and is forced into focus for no good reason other Isayama wanting her to be. She's just straight-up unlikable. Even if she didn't kill Sasha, I still wouldn't like her. She's just awful, and no, her being a child soldier isn't an excuse. The entire main cast of the series is made up of child soldiers, so people can fuck off with that argument.
You know, the more I think about it, the more I start to wonder if Sasha's parents just hated her, and that's why they took in the one that killed her. Nothing else explains it to me, and I am sick of people trying to defend it.
Imagine your baby girl joining the military for the sole purpose of making you proud, and not only blaming her for her death when she dies in the line of fire, you use her death as an excuse to speechify about the most retarded, nonsensical shit ever, and you replace her with the person who killed her.
That is some straight-up psychopathic shit, and it's completely, and utterly inexcusable.