MAD is defensive in nature. Putin isn't going to start nuclear Armageddon because the world won't let him have Ukraine.

It's time to call his bluff and enforce a no fly zone in Ukraine and state that the area of operations does not include Russia and that attacks within Ukraine do not trigger a NATO response.

So let whoever wants to help Ukraine send in troops under the banner of Ukraine's Foreign Legion. Putin is threatening the end of Ukraine's nationhood. This is a serious threat and warrants a serious military response from the free world.

Putin already said he considers the sanctions an act of war. And he hasn't nuked anyone. If he thinks he's already at war with everyone who is sanctioning him, then those countries are free to send in troops since they're apparently already at war.