#ac 103

Look at everyone's reaction in the office after Krzeminski's death. Peggy is shaken but she is very preoccupied with Howard's case. Jack is upset but seems generally resigned, chiming in only to say he'll call Krzeminski's girlfriend. Dooley is like a commander at war: he is not losing anyone else on his watch.

Daniel, on the other hand, was livid. Look at what he says:

Sousa: Really puts you back there, doesn't it? Somebody buys it, you realize could happen anytime, any day. How did it happen? Professional hit. Him and our only witness. Must have been watching us at the scene. I knew something was fishy about that anonymous tip. Who does that? Peggy: A concerned citizen? Sousa: Concerned citizens call the cops. This guy called us directly. It's not like we're in the phonebook. Somebody targeted them, and I'm gonna find that bastard. [Lines taken from here]

He is damn rageful at this figure who, from his perspective, is one step ahead of the SSR since the club in 1x01, who led to the death of one of their own (and it could very easily have been Daniel himself; he was the one taking night shift with Krzeminski). He wants to take down this culprit, almost as an act of revenge. Couple that with how he has always seen Peggy as an ally, as someone in his corner, putting her on a pedestal, is it any wonder that he explodes in her face when, to his knowledge, she turns out to be the traitor?

And that just adds another layer to one of the themes of S1: that everyone has a past, and everyone has blind spots because of that. Peggy was valued during the war but is now sidelined, so she is wont to see everyone as an obstacle. Jack hides a secret and is...a sexist prick, so he can't see why someone like Peggy would sincerely devote herself to what he sees as a lost cause, among other blind spots. Daniel is a more straightforward and steadfast person who doesn't play games that way, and that makes it hard for him to see past that sincerity, to pander to the drunk from the docks and to stomach Peggy's perceived betrayal.

Even us as the audience are blindsided. We watch this story through mainly Peggy's lens. Heck, most of us started watching the show for Peggy; we were with her in CATFA and CATWS! In the Agent Carter short! In her AOS cameos! We are predisposed to like her and to only see the events of early S1 from her perspective!