This entire situation is thorny as all hell, I'm not even sure which Cultures the Author is borrowing from aside from the hints of Ancient Greek and/or Roman, and even using those to try to figure out the optimal scenario here is iffy to say the least.
Doing something would give Dibel just cause to state his case against Almus before the king, but considering the wholesale slaughter of refugees fleeing the untenable life in the former's territory he'd need to be careful to not bring attention to that and highlight Almus' interference in a domestic matter. On the other hand, Almus not only has accounts of what goes on in Dibel's territory, but he witnessed the overly brutal way Dibel's own forces used to stop unarmed civilian refugees from entering his territory, he should be able to claim that he had acted in the interest of the crown, there's something screwed up going on in Dibel's territory, such mistreatment would eventually fester and explode into a rebellion against the Landowner and by association the Crown, however, before that happens, it could negatively affect the tax revenues that the territory would be sending to the Crown.
Don't worry, I recognise the latter bit there as utter horse crap, it's presumptive to say the least and will get Almus into a lot of trouble. This feels like a situation with the only winning move in the big picture of politics being that he needs to sit this out and just watch, but I have a feeling that the name of the commander and the fact that the refugee shouted for help might be important notes that would help him choose the right call for his future prospects.