Not sure if we should taunt a powerful dictator in the last third of his lifespan, who is slowly losing his war and his lifegoal of a reunited Russia. I know it's fun to humiliate a bad guy, but if he decides "if I die, the world dies", we're doomed.
If we let him win do you know how many other wannabe world rulers are going to try the same thing? And how many other countries this particular asshole is going to try to invade?
I don't want to let him win. There is s huge gray area between "okay, you win" and "go nuke us, coward": Good old civilized diplomacy, Star Trek-style! It's smart, elegant and everybody get's his/her voice heard. It's more difficult now than it was 2 or 5 or 10 years ago, and not as popular with voters. But I still hope the world is better than "let's kill the bad guy!"