I am the greatest advocate of the Constitution of the United States there is on the earth. In my feelings I am always ready to die for the protection of the weak and oppressed in their just rights. The only fault I find with the Constitution is, it is not broad enough to cover the whole ground.
Although it provides that all men shall enjoy religious freedom, yet it does not provide the manner by which that freedom can be preserved, nor for the punishment of Government officers who refuse to protect the people in their religious rights, or punish those mobs, states, or communities who interfere with the rights of the people on account of their religion. Its sentiments are good, but it provides no means of enforcing them. It has but this one fault. Under its provision, a man or a people who are able to protect themselves can get along well enough; but those who have the misfortune to be weak or unpopular are left to the merciless rage of popular fury.
The Constitution should contain a provision that every officer of the Government who should neglect or refuse to extend the protection guaranteed in the Constitution should be subject to capital punishment; and then the president of the United States would not say, “Your cause is just, but I can do nothing for you.”
( Source: Teachings of the Prophet Joseph Smith 326-27 )
It is important to understand Joseph Smith’s perspective. The U.S. Constitution promises Americans that they will have freedom to worship as they please, but nevertheless the prophet was persecuted for his religion all of his adult life.
Because of this persecution, Joseph Smith traveled to Washington, DC in November 1839 to appeal directly to President Martin Van Buren and the U.S. Congress. And he was told that for political reasons very little could be done for the early Latter-day Saints. President Van Buren told Joseph Smith that his cause was just but nothing could be done without losing the votes of the state of Missouri, where a lot of the persecution took place.