The ruins of Ammonihah were called Desolation of Nehors because it had been the teachings of the order of the Nehors that hardened the hearts of the people of Ammonihah to the point where they were destroyed (see Alma 16:11). The efforts of Aaron and his brethren to preach the word of God to a people following the same beliefs shows how very committed these missionaries were to the Lord.
Alma 21:19–23 describes one of the purposes of government—to allow the free exercise of religious worship.