The infected didn't have to be "dealt with" - that was the entire point of spending a full episode with Hershel going out of his way and nearly dying to cure a lot of people. Carol was wrong.
Dorian Thompson wrote:
Infinitely superior to the two previous Daryl/Beth outings.
This was an absolutely amazing episode. Top-5 for the entire show, very possibly the best episode The Walking Dead has done. Melissa McBride is an absolutely brilliant actress as Carol, and Chad Coleman, Brighton Sharbino, and Kyla Kennedy really really shined. Lizzie's utter cheerfulness at "Don't worry, she'll come back" and then how distraught she was, convinced she'd made Carol mad and not even processing what she'd done wrong was heartbreaking. Then the scene at the end where Tyrese forgives her... damn, powerful stuff to cap an amazing episode. Carol killing Lizzie is not comparable to murdering Karen and David (and she knows as much), but Tyrese made the right choice here. It's funny I was really annoyed when Carol showed back up because I expected the show to somehow try and justify what she'd done... but that never happened, and yet they found a way to deal with it effectively rather than sweep it under the rug.
Still, there's no reason to be insulting and call it "infinitely superior" out of some judgmental shipper loyalties.