This is what I've been trying to say....

 R.J. Rushdoony is not an unblemished voice in the concert of Christian social values: the conclusions that he held as orthodox and proper views would today result in his universal condemnation... and rightly so. But in at least this snippet of text he captures the essence of something very important. If you can free yourself from his misapplied labels of "conservative"  or "radical humanists" (think of them as little more than algebraic expressions, "A" or "B") we can see an insightful piece of societal analysis in the ongoing cultural and religious exchanges between Islamic and Christian faiths and the importance of defending creedal values.

"Every social order has an implicit creed, and this creed defines and informs it. When a social order begins to crumble, it is because the basic faith, its creed has been undermined. But the political defense of that order is usually made the first line of defense; it becomes the conservative position. But because the defense is politically rather than creedally informed, it is a superficial defense and crumbles steadily under a highly doctrinaire and creedal opposition. Thus, Cicero's defense of the Roman republic was a spirited and heroic effort, but it was also the epitome of impotence. The republic was already dead; Cicero himself did not believe in the religion on which the republic had been based. When Cicero could not accept the religious foundations which made an aristocracy sovereign, how could he expect to rebellious masses to accept it? Cicero's position was essentially personal, and the various defenders of the republic were more linked by purely personal tastes and interests than a creedal position. . . . . The conservatives attempt to retain the political forms of the Christian West with no belief in Biblical Christianity. Apart from vague affirmations of liberty, they cannot defend their position philosophically. The conservatives therefore become fact-finders: they try to oppose the humanists by documenting their cruelty, corruption, and abuse of office. If the facts carry any conviction to the people, they lead them only to exchange one set of radical humanists for reforming radical humanists. It is never their faith in the system which is shaken, but only in a form or representative of that system. The success of the subversive rests on their attack on the creed of the establishment, and its replacement by a new creed. When the foundations are provided, the general form of the building is determined. When the creed is accepted, the social order is determined. There can therefore be no reconstruction of the Christian civilization of the west except on Christian creedal foundations." —The Foundations of Social Order, R. J. Rushdoony, page 225-6