Yes, but We-The-People DO say that killing a living fetus after 58 weeks of gestation IS IMMORAL. Do you understand why this is a proper function of a representative form of government? And yes, 'We might' say this or that is immoral, but logically 'We might not'. That is the price we all pay for living in a democratic republic...We-The-People decide what laws we might and might not adopt via our elected representatives.
Finally, you raise the critical question, what is the 'true purpose of government and laws' concerning morality. Read the Preamble to the Constitution, it provides the answer you seek: “to form a more perfect Union, establish Justice, ensure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty.” We-The-People decide which moral constraints we put on government to attain this ideal society.
I have to let you know that I am not from USA, so I talk about such stuff in a broader context than just USA. When I'm talking about government, I'm not just talking about USA government. The USA constitution only applies to USA, one country amongst many countries of the world. Not having been brought up in USA, I don't hold any reverence towards the USA constitution nor the founding fathers of what is now deemed USA.
The document that you provided a link to starts off talking about God and God given rights. I'm not a Christian, I'm an atheist, talk of God and God given rights makes no sense to me. It gets worse, when you delve down that rabbit hole and you are told there is no compelling evidence and that you need to have Faith, and just believe. and that it is Bad/Wrong/immoral to be a doubting Thomas and virtuous to be believe without having seen. That is certainly no way to base a government and laws governing a society made up of many individuals of varying religions and non religious beliefs.
So if you are going to allow your government to force a moral standard on to the population. The question to ask is, "Whose moral standard are you going to force on everyone?"
If you go down that route and let's say you are a Christian, then you better keep making sure that you only elect Christian presidents, or else, God forbid, you might get Muslim or Hindu or Secular Humanism morality forced onto you (a Christian). But what about that pesky thing where there is supposed to be a seperation of Church and state? how is that reconciled with the idea of forcing someone's moral standard onto everyone in society. It seems to me to be the antithesis of the acknowledgement of having a society made up of a diverse population of empowered people living out their lives, making decisions, and navigating the complexity of living in society. Even in the Christian myth the idea is that people have free will, and the god wants people to make decisions and eventually the god will judge and reward people that choose "right" with heaven and those that choose "wrong" with hell. Taking choice away from the people seems to be removing that free will that the Christian god is deemed to be wanting the people to have.
But then it gets much worse, there isn't a set of Christian morals that all Christians agree to. There are Protestant Christians, Catholic Christians and other types of Christians, and if you delve further you will find Protestants don't all agree with each other, so who do you want to bestow the power to decide on what is morally right vs morally wrong and to be able to use the full force of the police and justice system to force this onto the people?
How are you to limit this all powerful president? The USA Constitution with all it's speak of God (presumably the Christian god) well that's convenient if you are a Christain, but what if you are a Muslim, or an Athiest, or a Bhuddist, or a Hindu or something else? Oh, but this country is a "Christian" country, founded by Christians on Christian principles, doesn't really cut it, it's convenient for Christians, but repuslive to non Christians. Perhpas USA should adopt the religious beliefs of the true founding fathers of USA, those of the native Americans, the American Indians!
In terms of what you said
"Yes, but We-The-People DO say that killing a living fetus after 58 weeks of gestation IS IMMORAL. Do you understand why this is a proper function of a representative form of government?"
I don't believe a society should be created where the majority can always outvote the minorities and use this to take away people's rights. Maybe this is convenient if YOU are one of the people in the current majority, e.g. in USA if you are a white Christian, but then you better make sure that your country remains majority white Christian. Maybe if you are worried you could go on an all out assault against immigrants, perhaps ban Muslims coming into the country so that your ways remain the majority view, and you have the votes to ensure your own moral standard is the one that is codified into law.
Myself, and somewhat going along with the concept of a Constitution which limits power of government and talks about some kind of "We do not receive the right to life, liberty, and property from earthly powers; we are born with these rights."
Well, of course our "rights" are earthly rights, we made them up, not some mythical god, but we made them up in a way by considering all people equal regardless of their ancestry, their beliefs, their colour, their sexual orientation etc. At least the USA founding fathers had the foresight to consider this concept, it is just unfortunate they felt compelled to inject their religious beliefs into this also.
Even in a fully Democratic system, if The People could vote on every law, it wouldn't be a good system, it would be a system where the majority rules over the minorities. Might makes Right. It would be a horrible system. Govt needs to be limited in its powers so as not to abuse the population and take away people's "rights" especially where those rights do not impact the Safety, Stability and Thrivability of society. Govt isn't there to be a moral judge or moral enforcer. If you believe in god, that should be the all powerful, all knowing god's job, not the job of government. If you allow Govt to dictate all this stuff, then you have no need for religious organisations as now it is govt deciding and enforcing what is right and wrong.
In my view, right and wrong should simply be something that each individual can decide for themself on. Religious organisation can exist and can try to convince people of their moral standards, people can argue and promote their own moral standards, these just shouldn't be enforced into law. No one wants a Nanny State. Let's minimise the influence of Government, let's limit their powers to trying to make a safe, stable and thriving society rather than trying to make a homogenous moral one.