I think if there was a way to answer in one sentence to the vast majority of liberal arguments of why the government should do X or Y, this would be the best answer from constitutional point of view:
In the famous case of United States vs. Lopez, it was argued whether the government has powers, under the Interstate Commerce Clause, to make it illegal to carry concealed firearms on school campuses. The argument that the General Solicitor (the government's lawyer) presented was that carrying guns on school campuses disrupts education, which eventually has an effect on commerce of the nation. Therefore, in an effort to preserve the national commerce, the government has a power to ban guns on the campuses.
The defense lawyer argued that the Congress has to make findings explicitly linking the banned activity to the interstate commerce, not a hypothetical that might affect interstate commerce. Furthermore, he argued, it is not within jurisdiction of the Federal Government to fight crime on campuses or protect education — that remains a State's prerogative, and when the Government tries to interfere, it is crossing into the State's jurisdiction.
Justice Kennedy asked whether the Federal Government can make it illegal to throw a firebomb into a school house.
Before the lawyer had a chance to answer, Justice Scalia said the text quoted above. Sometimes the concept of the limit on the government's powers means a limit on the government's powers to do good things as well.
Or what one considers to be a good thing.
This, then, is another argument that one can throw at the liberals. The reasons why the government should not regulate people's private lives in an effort to improve the society are:
1. It is pragmatically bad, because the government is plagued by all the problems of a central planner and cannot predict (as nobody can) how to distribute resources most effectively, how to regulate without creating perverse incentives and unintended consequences, etc. In short, when the government interferes, it makes things worse. Opposite from what it was trying to do. Therefore, distribution of resources and improvement of society is best left to private entities competing on a free market. This is an economist's argument.
2. It is a violation of people's natural rights. Even if something is a good thing, you can't violate natural law, in the form of people's natural rights, to achieve this good thing. It is naturally illegal. The function of the law is not to improve society, but to resolve conflicts. When the government attempts to do the former by interfering with people's private lives, it is not only misusing the function of the law but is in fact going against it. This is a libertarian legal philosopher's argument.
3. It is unconstitutional. The people simply have not given the government such powers in the Constitution when it was written. If people wish to do so later, they can do so by ratifying an Amendment. But until that has been done, the Constitution must be interpreted according to the original intent, because the original intent shows which powers the people and the states have clearly ceded to the government.
For instance, imagine I give you a job of cleaning my house under the arrangement that you only clean in the specific places that I told you to. Then, if you want to enter room A, you have to make sure I have given you explicit instructions to do so. If "situation has changed" and, say, there was a spill that went under the door into room A, you can try to call me and obtain my permission to enter the room A. But until I have given you an explicit permission to do so, it is unlawful for you to enter my property without a permission. The same way, under the Constitution, the government has been given a limited list of enumerated powers that the individuals and the States have delegated to it. If the government tries to do something that it was not delegated to, it is infringing the States' and the individuals' rights. This is a conservative constitutionalist's approach.
This is a good video about Justice Scalia: