@Maggot
From his own word, Hagure Metabo was worried the polarizing developpments at the end of the first volume (3rd in case of the manga) would be accepted by the readers. And the author is right : it's one of the most polarizing scene I've seen in a series so far.
In case of Robert, he knew from the beginning everything the Prince was doing was wrong, but he still followed suit... even when his father admonished him for what he was doing. If we let what he did to Elizabeth, don't forget he let his men attack villages and ra** women. Villagers who did nothing wrong and Haldoria would have faced no consequences for what they did (if not for Elizabeth).