Let's attack this argument at the source.
What actually
is Christian Morality? Obviously it incorporates God's Laws into it so let's look at those. Specifically, let's look at the biggest and most prominent
example of them in the 10 commandments:
1-4 are completely irrelevant here, after all even the Christian founding fathers saw that it was a bad idea to try and enforce those on people for many,
many reasons.
For the rest of them, let's look at the moral and logical basis for them. After all, God would not give an order that
has no reason to be followed. So we'll go in order.
5: Honoring your elders ensures a somewhat stable society, if you look to those that came for you for advice you most likely will build up generational knowledge and wisdom that will help prevent you from making bad decisions. Pretty reasonable, but not something you can really legislate, but instead must teach and encourage through public policies. No real intersection with freedom there.
6: Don't kill others unlawfully, ok... why? What makes murder wrong? It destabilizes communities and infringes on the other person's right to life. This is... actually pretty close to the NAP principles libertarians follow. Not exactly, but close to it.
7: No adultery, so don't lust after or pursue a married man or woman. For why this is a good rule to follow, we can look to the previous two: it destabilizes the group and society along with harming the victim (though in a different way than murder does).
8: Do not take what isn't owed to you. Put that way, it makes it rather clear what the base morality is here: it harms the person you take from.
9: Bearing false witness, aka: accusing them of crimes they didn't commit. Directly harms them and their freedom.
10: Do not feel, or rather do not
act upon, the emotion of Envy. Same deal as the last ones: it harms the victim and takes away from
their freedom.
All of these follow a very simple principle, one oft quoted by both constitutional scholars and libertarians alike:
Say what you will about some of his decisions while on the bench, but some of them were quite good. Others not so much, but most were still in the right
direction at least.
So if
Christian Morality follows this line of thinking then the question, instead of "what is moral?", is "where does the harm begin and what is the proper remedy to prevent that harm?" This is also the question more libertarian and utilitarian principles lead towards. Indeed, the only principles that do
not lead there are Authoritarian ones, where the question becomes "at what point does my control become too much to bear for the populace?"