Who is talking about a war? We are talking about a secession. Different things.
One will lead to the other. To believe that the leftists will allow the states that produce most of the food, as well as most of the oil and natural gas used on the continent (despite their incessant yammering on about the evils of carbon) to leave without a significant fight is very naive.
It'd be fun to use that as a wedge issue to "sell" the idea of secession, though. "Here's your opportunity to do away with fossil fuels in your communities and save the planet..."