Who cares who's wrong or right?
Riombara (and several others on BT) see Enweil as traitors to humankind. I think making your case against this is very difficult, and the only thing I wish to add is this: "Maybe it was just Enweil's turn to sacrifice itself and die with honour". Since the latter did not happen, however, revenge is warranted. You can argue left or right that Enweil did in fact not side with the daimons, but that's simply hallucinating. It's like arguing Riombara is not the richest realm on Beluaterra.
About IVF: who cares what the original purpose of IVF was or, in fact, whatever the hell IVF was? If Riombara recognized someone as the rightful heir to the land that used to be IVF, then Riombara will push such a claim in war - which we see happening right here. You can seriously whine on for weeks about how wrong Riombara's interpretation of IVF is, but that will not matter the slightest, because Riombara has an army to back up their argument and in the end that is how arguments in Battlemaster are settled.
It's very surprising by the way that Riombara is actually managing to win this war at the moment. Either its enemies are preparing some master move or they're really just weak. I believe in the latter and in addition I cannot wait to see more realm in the North get involved (on either side). Like, seriously, someone has to go remind Old Grehk that calling yourself an Empire whilst your realm is no Empire whatsoever is lame as hell and needs a good spanking.