Royalist reasoning sounds odd to modern ears, but please recall that most people who have ever lived have lived under monarchies, and, in those cultures, sacrificing armies and large portions of society, as well as destroying other nations, was a rational and equitable response to an egregious attack on the royal family like assassinating the heir to the throne. Yes, in royalist reasoning, or in the way of thinking that prevails in an established monarchy that has existed long enough for this way of thinking to become established, even an insult to the king or a prince is cause enough to go to war and end a hundred thousand lives of commoners and mere nobles.
The king, and his entire family -- royalty itself -- is preeminent such that even the highest of nobles is utterly incomparable with the majesty of the monarch or the majesty of any one of his family.
Only a royal has majesty, which is the highest earthly quality a human can have, and this is why "Majesty" is only used in royal titles and not in the titles of nobles.
The preeminence and majestic dignity of the monarch and his family, who share his majestic royal blood, places the monarch as the highest being on earth by far, not just different from all other, lesser humans in degree, but differing in kind, for only the royals have majesty and are absolutely preeminent among human beings. The greatest non-royal duke is, to a kind or a royal family member, like the lowest peasant or even outcast is to a noble duke.
They belong to entirely different orders of being, utterly different ranks of existence.