"What do you do when Russia says that every non-separatist politician in Donbas is a political radical?" Literally nothing. You're missing the point here. A

"What do you do when Russia says that every non-separatist politician in Donbas is a political radical?" Literally nothing. You're missing the point here. A NATO involved response would not end a Korean-style detente where troop positions etc. are a careful balance of power. This would be a collapse Russian forces in which Putin needs an excuse to run away and make it look like a victory. This is a game of 'hard power' in which 'public statements' are irrelevant, other than for propaganda purposes. Russia will invent 1000 reasons to cry after the fact, it's irrelevant once Ukraine is filled with NATO weapons and a bunch of forces and is 'NATO in everything but name'. Just like Russians do daily on state TV (it's comedically nuts) They can say anything they want, nobody will listen or care. Once Putin is gone, Ukraine will have to 'fear' about the same as Finland, which is not at all, so long as there are mechanisms in place and the state generally has order/power within it's borders. Now - if Ukraine has to do their own negotiating alone - then yes, it's a different story. Ukraine may have to subject themselves to a lot of BS and you may end up with a 'careful detente', and yes, in that case, Putin could literally use it as time to re-group and re-attack at the next opportunity he gets. That's unfortunately a possibly outcome in the current situation. But not if the West steps in, and ends it.