That is strange.  I've never seen it happen before, but it's my first game at 'genius' difficulty level on 2.0.

I was head of the United Planets.

The most powerful race in the game (largest empire) attacked me (I never saw the DoW, and there wasn't even one of those annoying double messages that disapears instantly) and I retaliated.  I later saw that AI was at war with everyone and they were a 'defiant race'.  So ok, I strike back.  I had already begun building some small fleets, so I step up production.   I have two full fleets of my own design, a third on the way and one fleet of basic corvettes.

So, I'm striking back.  System by system, planet by planet, I push back that pesky AI that's destroying all my starbases (they should be stronger, really, the AI is using technogically antiquated warships and it's running through all of them without a sweat, but that's another debate).   Right as I invade a planet - the AI is still the #1 out there, overall and in military while I'm second.

Here's the starmap:

https://drive.google.com/file/d/0Bw9mnPjp0Jm4UktpMW43Z1VkZ2M/view?usp=sharing

I'm the disjointed greenish one.

Next planet I invade, all of the major AIs declare war on me at once.

Is there some new kind of "bad boy" mechanism introduced in 2.0 that I missed?  My previous games were one difficulty notch under and I never seen it happen.  Can't just invade everyone in peace now?? 

It's really annoying, because I got caught twice with my pants down.  I was slowly building up to attack the Drengins but I got sidewayed towards the yellowish ones.  And I've signed open border agreements to everyone, maintained very good relations with everyone, so they have ships all over my territory.

If it's a bady boy mechanism, it's really badly implemented.  It should trigger according to some level of points representing your danger, and defensive wars shouldn't be counted as high as offensive wars.  What am I supposed to do, let the AI run all over me?