Referring to the opening post...I like it.
Rick has killed many people - either directly or not (remember orange back pack man). THAT is open to moral debate. I still think that is one of his worst "crimes".
He fancies her...why not? Crikey, in our current world many people blur the lines there (i.e. of what's acceptable).
He may still die at any moment and if she fancies him...it's not a big deal in a ZA world:zombies_neutral:

 

The way I see it, there's no law except the law of survival out in the world at large. Self preservation and the protection of your group is the main objective. Rick and his group obey that law but IMO they don't abuse it. Sometimes it comes down to it's them or us.

HOWEVER, each group that exists out there operates with a code of social norms that defines how they interact with each other within the group. Break those norms and there's a consequence. Two examples would be Joe's group beating to death one of their members because he lied. Guy broke their rules. Then we have Rick exiling Carol at the prison. She broke the norms the group had in place at the time by killing the living.

Rick and co. are not outside at the moment. They're playing in Deanna's sandbox now. Deanna has been running the ASZ since the ZA started and they have social norms within their group. Mostly unaffected by what's happened elsewhere, they run their community pretty much the same way they lived pre ZA. She's made it clear that those who don't assimilate can be exiled. She's interested in running a smooth operation which is why she's make Rick the new peace keeper. Macking on someone else's wife does not promote peaceful relations between Rick's group and the established citizens. What I'm saying is while Rick is a good person he's making a BAD decision here. He needs to wake up and smell the coffee before a really nasty situation occurs. I can imagine several ways that his can play out but as long as the ASZ stands none of them turn out well.