Our Founding Fathers were very clear about the necessity, purpose and function of government:
We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness.--That to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of the governed,
-- The Declaration of Independence
We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America.
-- The Constitution of the United States of America
There is much that both libertarianism and its cousin capitalist anarchism have to offer in social theory. There is also much that is wrong, at least, in what libertarian/anarchist thinking currently is. The root flaw of any such system is that it views man as owning himself. In fact, God owns man, and man has a duty to God.
This is why even though there are many libertarians who are pro-life, they do not have a consistent philosophy behind their conviction.
From this fundamental error, other errors come. Libertarianism does not recognize cultural, national and religious values as property in need of preservation. The jurisprudence is seen as based on consent, the flimsiest of all possible foundations of justice; economy is likewise seen as expression of the workings of the market, which leads to the intrinsic value of products ignored and long term thinking impaired (cf. our mortgage mess).
The author is correct that liberarianism has been merely an opportunistic ally of the conservatives.