Frankly, it's because we expended both our political capital and our nations by defending Polaris for years, and since we ended our treaty, we'd been told several times by NpO that even though you knew it was over, you'd still protect us when push came to shove. Then, when that day came, you were unwilling to spend a little political capital on STA when you were absolutely in a position to do so.
We'd never expect you to prevent us from being countered. That's absurd. Of course we should be countered by NADC's allies. But this? No. This is the sort of thing would wouldn't have been surprised to hear that you'd prevented once the war was over. Instead, we've heard that you approved of it. That's why we're disappointed.
Perhaps it's my fault. Perhaps I misunderstood.
Good luck with your wars. I hope it's all worth it to you.