I have a slightly different take. If they use a nuke, then they were always going to use a nuke. The difference between now and later on down the line how many times they used nuclear threats to get their way without consequences of a counterattack.

Troll and mock them mercilessly. Do not engage factually. Do not be hurt. They want frustrated engagement, librul tears, or both. Give them neither. Point out how stupid their take is. Change the subject to make it ad hominem. Gaslight. Move goalposts. They say ABC about vaccines, call them racist