I mean, it ought to be? Anyone from a Western background who actually knows the history of the Atlantean city-states would be somewhat disturbed by Orin's rather tone-deaf rulership. Yeah, fine, you didn't ask to be king and don't particularly want to be, but being a hero means that you've already accepted that the world isn't supposed to revolve around your ego (unless you're Batman), so frankly it really is not excusable that you don't know the history of the nation whose federal government you are head of state for.
I don't think it's so much that Posidonis, in particular its diplomats, don't know the history of Venturia so much as their knowledge hasn't filtered its way past King Orin's decision to not care.
Yeah, there's a lot of blame to go around there. The Justice League are definitely a bunch of people who could stand to listen more, as opposed to issuing dictates from a position of ignorance, somewhat ironic considering that Batman is supposedly a good investigator, Flash is supposedly a criminalist, Wonder Woman is supposedly a diplomat and Superman is supposedly a reporter. On the other hand, for an empath Paul is remarkably bad at reading a room and displaying basic politeness and discretion, even when not doing so goes directly counter to his desires.
In fairness Orin probably only got his info on Venturia from non Venturias so he doesn't know all that much.
He also may have gotten incorrect info if he asked the Venturians since they don't like him all that much and may think it was just some odd power ploy to get power over them.
Also while Batman is a great investigator this whole thing with Venturia was happening under the sea and it may have been difficult for him to investigate. He is a skilled detective but his skills aren't Tattletale levels of bullshit.
Flash is a CSI guy not a detective. Despite what TV would tell you CSI guys just analyse the evidence and what it is, they don't question suspects or make arrests or any of those things aside from just analizing scientific evidence, like chemicals and blood, not societies, relationships or politics.
Wonder Woman is a diplomat, but she was not called in to deal with this issue since she probably doesn't know all that much about Atlantean society and they may not want her considering she fought Clea in the past. She does engage in diplomacy like when she dealt with Rama Khan wanting to take his heir to his home in a diplomatic matter. Yes she attacked first but Rama was in earth monster form and attacking people, but when she discovered the truth she immedeatly went into diplomat mode.
Superman may not be a investigative journalist so much as he is just a guy that reports on the community and the Superman stories he writes which don't involve that much investigation since he was there.
Paul is an empath but he doesn't look too deeply unless he has to because it makes him uncomfortable and he doesn't want to coddle people and solve all their problems if they can do it themselves. The reason he is acting in a more insubordinate manner now is because he isn't bound by a magic oath, has recourses aside from the League, knows that they are flawed people that can make bad decisions and he doesn't need to please them all that much so that they don't become suspicious of him and prevent him from killing Nabu.
They also may be hesitant to get rid of him since it would be more difficult to monitor him and influence him.
And even if his actions brought Khan to Earth he couldn't order him to leave since Khan was apparently doing his job as a ring wielder, if not all that greatly.
If he took his ring Khan could still try to trade with Earth and legally speaking he would be in the clear.
Other aliens are already interested in the Earth, like the Thanagarian. At least its peoples will now have some experience in dealing with alien an alien polity before they interact with the big boys.
He probably also brought Earth to the attention of aliens even before this episode.
He is the founder of the OLC and a lot of people may be interested in him now and his planet.
Before anyone starts bitching about this harming Earth society and how it's his fault do remember he also helped end more than one tyrannical government and freed billions from lives of slavery and worse. Earth finally getting its shit together seems like a fair price to pay.
Oh and aliens were interested in Earth even before he came along. The Thanagarian and Apokalyps. Not the greatest civilizations out there.
