In the case of some, it's understandable: Father Gabriel and the survivors at the hospital have all lived fairly sheltered existences up to this point, and survival hasn't been all that difficult behind secure walls. For others, it's somewhat less so.
Gabriel and Dawn are two sides of the same coin. Still married to a world that's long gone, they're able to maintain that mindset because they've been isolated and protected in their little hidey-holes. This episode -- assuming we can take Dawn's remarks to Beth at face value -- sees them both uncomfortable with what has to be done but scared into going with the flow by the people surrounding them.
They're both also dogged by guilt, which is a recurring theme of the episode even among those who are coping better with the apocalypse in general: Father Gabriel's clawing at the floor has clear Lady MacBeth parallels, and immediately after ordering Carol essentially be put to death, Dawn provides Beth with the means to keep her alive.
What's puzzling is when you see this trend extended to Rick's group of survivors; Tyreese has embodied this for quite some time, making some downright confusing bad decisions out of compassion, empathy or a desire to hang on to humanity that is arguably no longer accessible. From refusing to kill the Terminus resident who then almost killed Judith, to suggesting that Rick should try to reason with the hospital staff in spite of a series of experiences that suggest that's a terrible idea, Tyreese's pacifist leanings has been a liability on and off this season, and tonight's episode definitely toggled that setting to "on."
The idea that there has to be something more to life than just survival is a recurring one this season; Carol was admiring art and Beth has been missing her music. The idea that the massacre of the Hunters/Terminians was going too far, was too savage, and disconnected Rick's group from its humanity is a notion that was played way up in the comic and became something to build off of for a while. That said, the comic rarely came across with the notion that in order to be "more human," one had to ignore the real circumstances in which one is living. Tonight's episode seemed to push that narrative on a number of characters, with varying degrees of success, and one has to wonder whether Tyreese might be used to play off of Gabriel and/or Dawn in the mid-season finale, perhaps learning to stike a balance of which neither of the others is capable.