Source: Alma 54

Ammoron’s logic:

17 For behold, your fathers did wrong their brethren, insomuch that they did rob them of their ^aright to the ^bgovernment when it rightly belonged unto them.

24 And behold now, I am a bold Lamanite; behold, this war hath been waged to avenge their wrongs, and ^ato maintain and to obtain their rights to the government; and I close my epistle to Moroni.

(Who started the king-men movement?  His brother, Amalickiah. )