Have you thought about this?
The leftists who are pushing hard for nuclear war to obliterate the world haven't really thought about the question.
Even if you delusionally believe that the war would only destroy Russia (because magic) you're still not following your own traditions.
The usual leftists, both secular and mainline "Christian", have a firm tradition about war. All wars branded by a Democrat president are good. All wars branded by a Repooflican president are bad. Vietnam was a good war when it was labeled with the LBJ brand, and IMMEDIATELY became a bad war when Nixon bought it.
In the transition from Bush to Obama, the tradition held firm. Iraq and Afghanistan were bad wars because Bush started them, but became good wars when Obama acquired the trademark. Ukraine and Syria and Libya are good wars because Hillary owns the copyright.
Bombing Russia should be a HORRIBLE war because it would be Trump's war from the start. No transition involved. Purely Trump brand. There's no way around it, unless you're certain that you can eliminate both Trump and Pence before you push the button.
Do you really want to be associated with a nuclear Armageddon that will be officially run by Trump, who is even worse than Nixon in your book?