I think we are, at least partially, in a violent agreement here. Both of us agree that Kenny had a point about the danger of letting Larry turns into a walker, that was necessary to at least try to save Larry (unfortunately, the options of conversation don’t let you try this middle ground) and that no waiting time would be enough to please Lilly (at least not until her father starts attacking us).
The big problem is Kenny’s posture after that. He may not be willing to die for someone who “doesn't put the safety of the entire group first” (like himself, for example), but he abandon the person always tried to defend him and his family and that even after what happened inside the meat locker was still trying to help him.
He might be very angry at that point, but that is a very stupid thing. If he do something to salvage the relationship… ok. I’m not discarding him as a total loss yet, but it became difficult to fully trust him after that.