iOnlySignIn
Prince$s
You can do the exact same exploitation with any other civ, not just France - all you need to do is to wait a few turns first.I'm pretty sure it's for gameplay reasons. Look at France; their UP means they never refuse to talk to you, and this is incredibly easy to exploit. Play as Italy if you really want to see this: no matter how weakened you are, France is never a thread because you can instantly buy off their DoWs. The same goes for attacking France: it doesn't matter how strong they are, as long as you can manage to conquer a single city. Then you pay them a bit of gold for peace to prevent them to strike back. (For this reason I think the French UP should only work from their side, not from other civs' side)
I hope you're not advocating using this "Refuse to Talk" mechanism to cover up flaws in other aspects of AI behavior (such as Peace making conditions). Because that is as effective and sensible as wearing thick makeup as a treatment to syphilis.
That said, French UP should definitely work only from their side. It's not like the Greek UP increases the GP rate of other civs, yes?