@DizzyDazzle I think that you got it wrong, jumped to conclusions but got something right, in a simpler way:
Put yourself in the Vice-Captain's shoes for a moment: someone who claimed to be the presumed-by-everyone-dead princess not only told him he was being lied to by all the court, including his direct superior (that he didn't look up to, to be honest), but that the very same kingdom he sworn to protect and give his life for was in truth corrupt, hypocritical and tyrannical which based it's claims in a complete lie. Everything that he believed to wasn't true. Can you really blame him to be "a little" skeptical, even coming from the alleged princess mouth?
Also, he wasn't trying to kill the princess, he was neutralizing her. Sort of like arresting her. Due to the weight of her accusations, he did the sensible thing in his eyes and instead of believeing her from the start (he went along with the charade, that's something) he wanted to take the thing to the one who might clarify the issue: the king himself. Problem that we know but he doesn't: taking her back to the castle is a TERRIBLE idea; but he's a knight. He answers to the king before anyone, even the princesses. That's where the line "I don't care about justice" come from. If his liege says right off the bat that the princess Freia is false and has to die, he kills her, no questions asked even if he KNOWS that it isn't right. And attacking her is because things got out of hand, as Freia knows that going back is suicide, so the VC has to neutralize her by force.
But yes, I agree that the high post in court are wither complete psychopaths that knows the truth and not only agree with it, but revel in the debauchery, like the former Knight Captain or Norn; or blissfully ignorant of the ways of the kingdom thinking they are the "good guys", like the Sword Princess (not that Sword Hero bitch).