The standard of liberty was the call to defend the Nephite way. This is precisely what this mission is intended to do. Moroni wants to remove the kingmen, which was the group against whom the title of liberty had been raised in the first place. Now as he marches to Gideon he attempts to augment his battle-hardened troops with other reserves who are in the country round about, and who are willing to fight for freedom, which is defined (in this case) as the traditional Nephite way of government and religion.