But it is Player B's objection that makes him mistaken. If Player B did not object, Player A would be on solid ground. So is the problem Player A's decision, or Player B's objection? That is the problem with trying to find fault in this situation.
If the problem is that Player A's actions are objectionable, and the definition of objectionable is that Player B objects, the "problem" is that Player B objects to Player A's actions. It's circular logic. We need some definition of acceptability outside whether Player B objects. We need some measure of whether their objection is reasonable, and whether their request to remedy the problem is reasonable. That is equally true of asking Player A whether his presumption is reasonable. If the root of the problem is that Player A and Player B simply want different things, that is simply a conflict. It does not seem fair to resolve it in favor of Player B based on the arbitrary criterion that we are considering Player A's stubborn refusal to be the cause rather than Player B's stubborn refusal.
You are asking for an objective, universal standard for social situations and interpersonal relationships, and it just doesn't exist. As I was saying in the last page you cannot account for all situations without knowing the context, the people involved, etc. There are too many unknowns here for us to decide if Player A is just being stubborn or if Player B is just being overly sensitive. In some groups or situations, Player A is at fault, in others Player B is at fault.
Among my friends I know we say things that strangers might consider offensive. For us, "I hope you die on your birthday" is basically Hello. And sometimes the things said involve race, ethnicity, or whatever, and in most other social situations I would probably consider horrifically offensive.
And, yet again, I would like to bring up that a large reason for the number of responses against Player A was not his attempt to role-play, but rather the response to hearing Player B's taking offense by insulting and demeaning Player B.
So as a GM, I would ask the players to "come to the table," that is, to act with good intent toward all. If no truly satisfactory solution is available, then I am left wondering, who has the greater willingness? Whichever player is less likely to leave the group despite not getting what they want is my preferred player. If Player A simply opins, "This sucks" when asked to retcon the emotional attachment, while Player B says, "This is unacceptable and you must stop at once," Player B has signalled their willlingess to terminate the group. Player A, however, has only signified they will be unhappy with the decision, as they continue with the group. Since Player A has signalled a willingness to continue and Player B has not... I choose Player A.
No pistols at dawn?
Obviously the context may not fit what I have filled in, but there it is in a nutshell, as I see it. It's kind of a shame that Player A does not have to compromise if Player B quits, as that might be a useful learning experience, but that is Player B's doing by quitting.
If I may put on the Psychologist hat for a moment (knew this degree would come in handy one day), in any group dynamic of two or more people there are going to be varying roles of dominance and submission, winners and losers, with tons of compromises going on constantly. As conversations and other social aspects flow there are going to be people who control a conversation, then give up control, then re-establish it. This goes into all manner of aspects, where you go to eat, what movies to go see or what channel on TV, topics of conversation. And unless you have one really dominating personality this control cycles throughout the group. So in any group you are constantly compromising, giving up, but also gaining, control of various situations. And 99% of the time you barely notice it and don't really care.
This situation is just one of those. We, being the analytical, overly strategic nerds that we are, are examing every possible aspect of this scenario over the past (believe it or not) two weeks. But in reality, in most groups this 'conflict' might take 30-60 seconds and could be as easy as:
Player A: I profess my love for [Player B's PC]
Player B: Hey, I'd prefer we not go there. I'm just here to kill orcs.
Player A: Eh, fair enough. Hey DM, can you throw in a love interest for me at some point?
OR
Player A: I profess my love for [Player B's PC]
Player B: Wait, what? When did this come about? I'm not too sure I'm cool with this.
Player A: Let's give it a try, I promise not to get weird but I think it could lead to some fun story lines.
Player B: OK, but just remember I have class.
Or some such. The majority of times when these kinds of conflicts come about in social situations one side will usually give in, and not really even consider themselves to have 'lost' the conflict. This is the only way group dynamics can work, otherwise every decision no matter how insignificant could end up as a brawl (what do you mean you got Diet Coke???)