I do not think we have a treaty with purple stating we all head to war together. I understand why people are angry we did not side with purple in this war, but there are many other spheres in this situation. Aqua with Nato, Orange with IRON. While we had treaties with both sides in this war, we knew our alliance had to help defeat NPO due to our past history with them.
bottom line, we will gladly leave purple after the war is over if the purple alliances insist. Hopefully driving people off spheres for having different ideas becomes a thing of the past after this war. But so far it doesn't sound like it will be.