Rick's misguided, sympathetic stand was all for nothing.
I got to say I don't see it that way. Carol did what she did to prevent contamination from spreading, which was ill conceived, because it spread anyway. A wise person would know that was happening. The point of survival in a group should be to give everyone every chance to survive that you can. Would Karen have survived? Not likely, but that's not when you put a person down, & it wasn't why Carol did it
You don't leave people for dead or put them down just because things aren't going your way. That's what... The Governor does. What Rick did was a matter of principle. In this kind of survival mode, you're only one corner away from a situation going badly. You can have no unity if you know that a unit member is one bad turn away from ending you for whatever greater good they perceive. That was the problem with Shane & to a much subtler degree, it was the problem with Carol