Yea, that doesn't look like the AI was very happy.
Assuming there weren't 5k units in the system you hit (unlikely given the in-game time), that would seem to be unintended behavior.
The planet was a level 3.
One thing i noticed was the AI threw up an ION turret which wasnt there, before. Hell they threw up a ridiculous number of turrets.
*Edit* The ai responded with 1.7k anti starship units i don't think thats normal ether?
*EDIT* 2 More things.
1. The AI Progress modifier window does not reset, inbetween games, such i start a new game it still has the previous games messages up.
2. Would using a handicap make the AI go insane?
*EDIT 2* I attached a saved game, i can pretty much reproduce it constantly.