They went for sensationalism, and while a bit over the top with violence, it was pretty much accurate to the comic which was interesting. I did not think they would be able/willing to do that. The blood effect is really no different than we have seen in how many horror or action (300 had more spatter per camera shot) movies. The Saw franchise is way worse for gore IMHO. If it was only Abraham that was whacked then I wonder if it would have generated as much of a response?
In any case, I am willing to bet that a lot of the people that are stating that they are done with the show online will be back at some point to see how they get revenge on Negan (they will likely be disappointed if the TV show sticks to the comic with this........). After something like this, the need for punishment of the perpetrator will draw people back.
FWIW, I was really hoping that Daryl would get whacked as well as I grew tired of his character a long time ago, but c'est la vie. Looking at the love fest they have with him and the way the story line is shaping up now, he has just as good of a chance of replacing Negan as Dwight does, unfortunately.