I wonder if the sheer amount of methane dumped into the atmosphere from the damaged pipelines would be an acceptable cost for the hypothetical GreenWar? I couldn't see it, myself. The pipes weren't empty, and thats a lot of quite bad greenhouse gas now making things worse.
It's a tricky calculation for sure. Depends on the likelihood and duration of those pipelines ever being used again, and the take-up of alternate, renewable energy sources - or just doing without.
However, considering the war and today's sabotage purely from a global warming perspective, it could be net positive in the long run. Accelerating the transition away from fossil fuels.