It's because of rick's "we don't die" line that really takes hold once they get to alexandria. Before, when dealing with the prison and the governor and being outside, they got used to hardship and death and whatnot. By the time they get to alexandria, the only people dying are new people...people not really in their OG. The brutal beating in front of them in the comics is to an Original member of the team....one of the "untouchables." When those that you believe are untouchable actually get hurtt, and in this case brutally killed, it makes you realize yet again how mortal you are. Rick's group might be fighting for its life, but against the walkers they generally feel it's a forgone conclusion that their original group will live on. Seeing that immunity to death slowly crushed in front of their eyes is traumatic in a way past loved ones dying may not have been. Add to that the fact that they can't immediate retaliate? That they have to not only see that death but say "thank you" afterwards? It's enough to make them throw up twice. By far the most meaningful and traumatic death in the show/comic. The only one that really comes close is maybe the Beth death from the show because they were so close to having her back safely.

Imo, that's why this death shouldn't be abraham. Making it abraham would kinda be a cope out to the importance of the death since abraham was a tag along and gives them somebody to kill off part way through the season at the same time (since he is already outliving his comic life at this point with a distinct lack of arrow in the back of the head). For this death to hAve the right feeling it needs to be someone that is DEEPLY cared about. It needs to be maggie, glenn, or Daryll. If I had to guess atm, I'd actually lean towards Maggie at this point because of her actress crying, the fact that killing glenn kills off the only Asian character on the show (something tv viewership is going to look at in ways a comic might not), and daryll just being such a key difference between the show and the comic. Especially with how out of place the guy playing dwight seems, I could see Daryll becoming the leader of the saviors by the end of all this. Also, in the comic's, maggie has a child but Judith is already dead. Seeing as Judith makes for a distinct lack of a need for a surviving baby character..... Tbh though, they've done a very good job giving most or all of the characters availble to be killed death flags over the last few episodes...any of them have logical reasons it could be them.