Well, I'm not sure if they did anything wrong, considering that:
1. The Phantoms kind of shown disdain to the RHA a couple months back by deciding to openly praise Corsairs during a battle in Omega-5, while at the same time insulting RHA forces. High command was informed, and the Phantoms were declared as an ally of the Corsairs. No messages from them followed, so the status is still unfriendly to hostile, and indeed not neutral. Check the RHA faction status.
2. The RHA is both a ideological and a pragmatic faction. Piracy is done for two reasons: to undermine the corporations, and to keep the movement well supplied. Nowhere does it say that the RHA doesn't pirate, it's just that it doesn't do it very often (which is how it is in game), and that it is not its main mission.
Now, the RHA being former miners themselves, why would they let other miners who are being sent by greedy corporate CEOs get killed by some guy in a Praetorian (ship of arguably their biggest enemy at the present moment) flashing the IFF of a faction that has shown and admitted to the RHA that it has dealings with the Corsairs? The point isn't to kill all Kruger and Daumann, it's to hurt those who run those corporations, which means cutting into their pockets. Doesn't mean that the people that they employ need to be executed on the spot. Hence why I see nothing wrong in what happened, and I think it was kind of in RP...
Just not sure what to do about this "miners switching to their RHA when they see foreign pirates in O-11". Technically it's kind of logical that you would attract that kind of attention, as Freital is right next to the mining fields, and it would score brownie points for the Hessians among the "people", as well as get them some funds no doubt. All in all, the Hessians win the most in that case, and they basically control that system anyway so a patrol would stumble upon you. I'm not sure if this switching constitutes metagaming or not, that's up for discussion I guess, but then again I am not sure if it was switching at all in the first place. The first set of screens simply looks like an unfortunate coincidence for you that they happened to undock while you were there. The second set I'm not sure about since it only shows that one of my recruits has very good RP skills, so meh.