1. Absolutely no diplomatic relations should be automatic except for neutrality to a new realm. That is bad game mechanics plain and simple. If a federation want's its policy to be war with any realm that breaks from the federation that should be up to the players of the ruling characters to uphold the treaty.
2. I shouldn't have to consult the wiki every time I do something. When other realms broke from federations the message was "War will likely commence" which suggests that they have the option of not declaring war. When I joined the Federation it did not inform me in any way that the federation would be unbreakable.
You are, of course, entitled to your opinion, but that doesn't change the fact that a) federations do this, have done so for years, and are not going to change just because you don't like the auto-war declaration that is an intended part of the feature, and b) as ruler, it is
your responsibility to familiarize yourself with the options you are using.
It may not be reasonable to require all 1000-odd players to read all the manual info on the Wiki, but I do not believe it is at all unreasonable to require those very few players who have attained the
highest position in the game to learn what the buttons they push are going to do before they push them.