I'm not sure this is a situation where talking outside of the game is necessary. It doesn't sound like they had a disagreement as players, but as characters. Changing an aspect is useful, but what I would have had happen in this situation is I'd have compelled your high concept for you to start a social conflict with the other members of the party to try to convince them to not attack the ghoul. Remember, this isn't D&D, and there are actual social mechanics for characters with different agendas to work out their differences. Its not D&D, and as such, a lot of things that aren't good for such a game are very good for this game. Intra-party social conflict is one of those things.
I wasn't there, so I don't know the exact situation, but I want to emphasize a distinction. If the group, outside of the game decided, "Hey, we have to kill this ghoul because thats all we know how to do" then you have a group dynamic issue and talking to them is your best way to go. If each member of the group instead said "Yeah, maybe we could talk to the ghoul and rehabilitate it, but my character wouldn't do that, so its not happening" then it is 100% perfectly fine and acceptable for them to act that way, and you have an in game social conflict and please oh please don't run away from in game social conflicts with the rest of the party because it really enriches the experience.