So the philosophers who drafted the ideas around our Constitution were rooted in midieval thoughts ... that "Divine Rights" and absolute monarchies were contrary to God's Laws and were inconsistent with a properly-functioning society.
Is the author saying that libertarian thought and traditional conservative thought are often inseperable because the former is based on concepts that are directly derived from the roots of the latter?
There it is in a nutshell.
There are many fascinating histories of English Constitutional development in the 17th Century.
There you will find the massive roots of the American Liberty Tree.
He papers over the chasm that separates the two world views by asssuming that libertarians share his position that Western political liberties are rooted in Christianity. The many FR debates on this subject demonstrate clearly that many, if not most, libertarians consider Christianity (as well as all other religious traditions) an impediment to freedom and not a root resource.
It has been my experience here, w/ some exceptions, that the libertarian position is at its most fundemental level atheistic in nature and for this reason is diametrically opposed to a traditionalist position as layed out by the author. In fact, I have seen the libertarian interpretation of western history defined in the exact characteristics assigned by him to liberals.
The only common ground shared by the two groups is a desire for a smaller/weaker central government, but even here the roles and responsiblilities that each group feel are legitimate government functions vary greatly. I really don't see a practical reconciliation between the two groups nor do I think that libertarians bring all that much to the party (political or otherwise).