I don't see anything bad in losing in a fair fight. The problem starts when one group obviously ganks the other, no matter if for ooRP hatred (wait, someone hates us?) or just to ruin someone else's fun.
I have a simple solution for ganking (or situation in which the only goal is to destroy meet-and-RP scenario): first, we politely ask people to not to do that, but we continue our roleplay with that group. Secondly, if they after several tries of ganking still do not get the point, we limit roleplay with that group and put inRP consequences.
The very last form is the situation in which that exact group (or players) are not invited (i.e. are banned to participate) to any events held by us and other party - moreover, we may refuse interaction with that group inside our roleplay (in other words: KoS label).
Thankfully, I have never seen anyone reaching the last form. Yet.
