We still have Mutual Assured Destruction, MAD. Running Russia up against a wall has to be better defined. Russia wants Ukraine as a client state and a buffer, like Belarus which is a neutered pussycat. Ukraine doesn't want to be Belarus, it wants to be Ukraine allied with NATO and a part of prosperous Europe. NATO in Ukraine might make Russia behave a little better. Crimea would still have to buy its electricity from Ukraine.

But the "nothing to lose" bothers me. I don't see the US invading all or part of Russia, no one has done that successfully, and for what purpose? The only thing Russia would have to lose under any foreseeable circumstance is their very existence after a nuclear exchange.

Plenty of Democrats (myself included) have taken various administrations to task over invasion of other nations. Opposition to stupid wars is what we do, and Republicans, in general, do not.