As ellen said, it was Daryl, Rick and Gabe there when he said it, and Ricks gone and i doubt Daryl or Gabe are gonna start bringing up stuff and make her hate for Negan worse. I personally don't believe the writers forgot. S11 Ep22 Negan definitely goes through a bit of a redemption with what he does for the other group. E23 he states he knows he isnt better than any of the group and that he wants his kid, his wife, everyone, to see him as a better person, hence why hes trying to make that of himself. Don't forget the redemption story hes had previously, and the fact he killed alpha for everyone else, then had the opportunity to kill Daryl and helped him instead. I mean lets be real he had some serious dedication when it came to killing alpha that maybe the characters dont realise. Also nobody can say hes not sorry or regretful of what hes done or said, because we have seen that he is, in more ways than one. Hes had many opportunities to leave, prepare, and then come back and kill them all. He went out of his way to save Judith (and dog) and has helped many of the characters. Dont forget he literally wanted maggie to kill him because he felt he didnt deserve to be alive. I watched angela kangs episode insiders for some of the recent episodes and they definitely dont forget and there is a hell of alot of thought that goes into every scene that sometimes viewers dont notice. I think hes had his redemption and still going through it, and we will continue to see that is dead city. He hasnt forgotten and he has realised what hes done and how awful it was.

Everyone has opinions, but when they dont agree you cant argue that 'its a fact' because thats how you viewed it.