Why is it when playing against the computer AI, and you research your culture spread up to where it can entice "rebels" to randomly attack your opponent...

The Rebels do not do a thing, at all...

They show up at the opponents planet, and then they just sit there, and do nothing and the AI's ships ignore them as well...then when I get there to take the planet away from the AI, I've got a swarm of rebels there that have slowly accumulated, and then attack me when I show up, as well as the AI's ships to deal with.

With that said, I have witnessed countless times, when the AI just sails straight through the pirate base, and the pirates do nothing to them, just ignore them... but when I enter, they swarm me.

Is there a specific setting that I am missing that effects this behavior?