First, we should doubt the source, since the actors' own Twitter account can't be completely trusted (why would you pull a whole episode instead of just the controversial scene? what if it was just a promotional resource?)
Prior to the release of the episode some sources echoed Cudlitz's account and wondered if it could be violence, sex, cannibalism or the F-word.
Even after the release of the episode, it was unclear if or what was wrong with it. What could be "too much" in a show about zombies?
So my guess is, as this source says, that
Cudlitz was probably just exaggerating for the sake of a good tease
There is no official explanation from AMC, all websites you could check about the issue can't give you a plausible reason, even after the release of the episode. There is a source which stated (prior to the release) that
(The) episode of The Walking Dead would have a VERY difficult getting past the censors if they follow along with the comic book series.
But that is just more guessing. The comic event they would be referring, and that supposely might be too much for the censors would be
A flashback, in which Abraham’s family is hiding out at a grocery store when he decides to go on a supply run. When he returns, he finds that his wife and daughter have both been brutally raped and the assailants have forced his son to watch the whole thing.
But something like that probably would have been addressed by scriptwriters or executives from AMC long before a "censor" would have anything to say about the matter.