Let me cut my nose off to spite my face

I saw this briefly mentioned on NHK news earlier today, and now it's at Reuters:

The leader of Japan's tiny Social Democratic Party [Mizuho Fukushima] threatened on Thursday to leave the ruling coalition if her views on a U.S. military base were ignored...

Surely this is just a bluff; just a negotiating ploy, for the SDP would not take a chance on damaging the coalition and perhaps reviving the snake.

Or, could it be explained by Chie Nakane's view of groups in her book Japanese Society?* Sometimes when these sort of things happen, I am tempted to turn to those sort of cultural explanations to rationalize the seemingly irrational. But sometimes, the irrational is simply irrational.

*This is a short book that I think is still worth reading even though it is now decades old. It was recommended to me by one of my university professors who told me that in order understand Japan I should read that book. He was a Japanese fellow who did not subscribe to the theory that non-Japanese could never understand Japan. In fact, he had a reputation for insisting that students in his class did their damnedest to do so. And he was a grammar-nazi too.