Punchline: You can make any argument you wish. If you quote from a distinguished source, you had better be sure that you have good reason to believe that there are not other quotes from that same source, or other interpretations of the quote, that turn against you.
My problem with how people use Clausewitz, and with Sun Tzu, is that they would seem to provide quotes for whatever position people want to take, or you can find quotes in them to show they are wrong. I take comfort from Pope Francis, who has announced that matters of doctrine (homosexuality, abortion, contraception) should take a second place to doing good, including people in the faith, and helping the poor. See below for more on the Church and doctrine.****
From Wikipedia, my underlining and bold:
Carl Philipp Gottfried von Clausewitz (//; July 1, 1780 – November 16, 1831) was a German-Prussian soldier and military theorist who stressed the "moral" (in modern terms, psychological) and political aspects of war. His most notable work, Vom Kriege (On War), was unfinished at his death.
Clausewitz espoused a romantic conception of warfare, though he also had at least one foot planted firmly in the more rationalist ideas of the European Enlightenment. His thinking is often described as Hegelian because of his references to dialectical thinking but, although he probably knew Hegel, Clausewitz's dialectic is quite different and there is little reason to consider him a disciple. He stressed the dialectical interaction of diverse factors, noting how unexpected developments unfolding under the "fog of war" (i.e., in the face of incomplete, dubious, and often completely erroneous information and high levels of fear, doubt, and excitement) call for rapid decisions by alert commanders. He saw history as a vital check on erudite abstractions that did not accord with experience. In contrast to Antoine-Henri Jomini, he argued that war could not be quantified or reduced to mapwork, geometry, and graphs. Clausewitz had many aphorisms, of which the most famous is that"War is the continuation of Politik by other means" (Politik being variously translated as "policy" or "politics", terms with very different implications), a description that has won wide acceptance.
****I take comfort from Pope Francis, who has just announced that matters of doctrine (homosexuality, abortion, contraception) should take second place: to doing good, including (rather than excluding) people in the faith, and helping the poor. The last two popes were rather different than Francis, their having put lots of energy into doctrine and also encyclicals of that sort. What Francis is doing is saying that doctrine, drawn from the New Testament and earlier Church teachings, is being used rather selectively and so letting the faithful avoid the true mission of the Church. His taking the name of St. Francis, this sounds appropriate.
Many years ago, I knew John Noonan, appointed eventually by Reagan to the Appellate Court, Ninth Circuit. Noonan was a professor of law at Berkeley, and wrote big books on canon law and history. He did a big book on contraception, showing that the Church had had various points of view on contraception, and varying emphases on it. Similarly, John Boswell did a book on homosexuality within medieval Christianity, again showing how changing was Church doctrine and practice. In general when you know lots of history, the sureness of what you draw from documents and text tends to disappear. Hence, the originalist position of Judge Scalia of the Supreme Court, depends to some extent on what we know of Early American History. I always wonder if Scalia would change his position on various issues if we discovered documents showing that the plain language of the Constitution meant something very different than what Scalia takes it to mean. Similarly, the same issues come up in musicology when people aim to have authentic early instruments and styles. Richard Taruskin has shown how problematic is such a presumption.