"Having the U.S. risk global nuclear annihilation over Ukraine is an indescribably insane view, as one realizes upon a few seconds of sober reflection."

No, it is not. Loosing Ukraine to Russia means imminent danger to whole Europe and from there U.S. This war is existential.

Letting Russia know that nuclear retaliation is very real possibility forces Russian establishment to reconsider current situation and options.

Putin may be (or maybe not) crazy, but the whole Russia is not and Russians understand real power very well.

I prefer not to die in nuclear Armageddon, but I do not want live in Europe constantly threatened and sliced or worse, concurred and destroyed by Putin.