Beyond any other thing, the purpose of the First Amendment is to ensure that the nation may flourish by having an open marketplace of ideas.
The First Amendment protected three major things, speech, petition, and religion. The central, uniting principle behind these is an observed tendency of governments to attempt to influence what the People think and believe, and to keep the government out of such matters.
The primary purpose then, of the First Amemdment, is to prevent to exploitation of government power to control the minds, thoughts, and beliefs of the People. It is rooted in the principle that the government may regulate actions, not thoughts and beliefs. It is a principle that every idea is worth discussing, and that laws may change in response to changing beliefs.
The protection of religion in the First Amendment shows this principle was intended to protect the People's private beliefs from governmental interference, yet we have not upheld that as a society.
Governmental power is regularly extended towards snuffing out ideas contrary to the current administration.
Ideas and media around sexuality are often regulated in the name of establishing a morality code. Obscenity laws are fundamentally an attempt to install Christian values into the law, not a legitinate exercise of state power.
It is often repeated for example, that such content is "harmful to minors", but what harm is there? Scientific evidence has not shown that exposure to pornography is inherently harmful. We have seen some effects, for example the tendency of pornography to increase sexual promiscuity, but such a behavior cannot be considered "harm" unless you subscribe to a Christian religion derived worldview on the morality of sex and monogamy. Other effects have also been noted, such as a decrease in rape and sexual violence in countries with more widespread access to pornography.
It is difficult to conclude that any of the obscenity restrictions are based on any rational, sound, and religion-neutral values.
A rational, secular society might better leave such morality decisions up to parents, rather than the State. It is what the founding fathers would have wanted, a society free from moral coercion, where the governmental power is to protect citizens from being injured by others, not to establish a religious moral code into law.
That is not to say the State should never instill moral values into its children, but it should only be done when there is a rational and secular basis to instill such behaviors.
Societies like Japan flourished with very different ideas on sexuality than the US, and no harm occured to them. We ought to learn that society doesn't collapse when you don't follow Christian morals.
Such abuse of governmental power is a type of tyranny whereby the Christian majority attempts to force non-believers into submission into their moral sex code.
It is sometimes cloaked in the guise of being justified by secular motivations, but such facades do not withstand scrutiny. It is unfortunate that the Courts are largely staffed by religious persons who cannot distinguish their deeply held religious morals from ones with a rational basis.