Mormon understands the real threat of Amalickiah, even though his followers did not. First and foremost Amalickiah was a threat to the church of God. Even though he was attempting to be a king, the ultimate problem was not political, but religious. The type of kind Amalickiah wanted to be would be destructive to the underpinning egalitarianism of Nephite religion. With that principle destroyed, the destruction of the rest of the belief system might easily follow when the society adopted the religious ideas that propped up Mesoamerican kings and their hierarchical societies.
It is unclear how Mormon saw this threat as a specific threat to “the foundation of liberty.” It is probable that he is specifically speaking of the liberty to believe in God, something that he sees being threatened. Certainly the new king as a political leader would not have less liberty that did kings Benjamin and Mosiah. Even in the Mesoamerican hierarchical society, the kings provided benefits that the people wanted, or the people would discontinue servicing the kings. Indeed, it appears that at the end of some cities, this was precisely the situation. The kings no longer served the needs of the people, and so the people simply abandoned their kings and the whole city-hierarchy behind them. (see the analysis of the end of dynastic rule at Copan as discussed in David Drew. The Lost Chronicles of the Maya Kings. University of California Press, 1999, pp. 348-9)