Catholics who object to libertarianism tend to base their objections upon misunderstandings about what libertarianism is.
Complaint #1: There is more to life than liberty
One complaint is that libertarianism is insufficient as a guide to Christian life. In other words, the critic claims (rightly) that the non-aggression principle is not the answer to every question. In this objection, they fail to grasp that libertarianism is not a complete blueprint for anyone’s life, but only a commitment to avoid the initiation of force against others. The issue is not whether libertarianism is sufficient, but whether it is consistent with the Christian life. The essence of that life was summed up by Jesus in these two commandments:

The first is, ‘Hear, O Israel: the Lord our God, the Lord is one; you shall love the Lord your God with all your heart, and with all your soul, and with all your mind, and with all your strength.’ The second is this, ‘You shall love your neighbor as yourself.’ Mark 12:29–31.
This first commandment—which deals with one’s relationship with God—has no relevance to the non-aggression principle.
Jesus’s second command regards our relationship with our fellow man: “You shall love your neighbor as yourself.” This command contains the non-aggression principle (NAP) which is exactly equivalent to that aspect of the commandment which forbids our doing to others what we would not want done to ourselves.
The critic will charge that there is more to loving one’s neighbor than not harming him: What about feeding the hungry, clothing the naked, visiting the sick, forgiving and praying for our neighbor, and so on through each of the corporal and spiritual works of mercy?
As noted above, however, the issue is not whether the NAP is complete, but whether it is compatible with loving one’s neighbor. Feeding a beggar may be more praiseworthy than not stealing the beggar’s lunch, but the second is as necessary as the first. There is nothing in the NAP that conflicts with the Christian duty to good deeds, charity, and kindness. There is no point in criticizing the NAP for being an incomplete system of morality when it makes no such claim of completeness for itself.

Other critics of liberty will point to the conduct and writings of certain libertarians as proof that a Catholic cannot be a libertarian. Doubtless, some libertarians practice and approve of conduct that Catholic teaching reproves. These may involve sex and marriage issues, drug use and other abuses; literally, every wrongful choice that people make that does not violate the non-aggression principle.
Again, the critic expects too much of liberty. Libertarians understand freedom as necessary for human flourishing, but no Catholic libertarian considers it a gameplan for his life. To leave one’s fellow man in peace is simply St. Augustine’s common ground to which all must adhere. Nothing in this principle is contrary to the Catholic faith.
In the next post, we will consider those who argue that Catholics cannot be libertarian because libertarians are selfish individualists.