From my favorite theologian, Calvin, with a bit more on the part about "does not nature teach ..."
http://www.ccel.org/c/calvin/comment3/c ... /xviii.htm
Doth not even nature itself.
He again sets forth nature as the mistress of decorum, and what was at that time in common use by universal consent and custom -- even among the Greeks -- he speaks of as being natural, for it was not always reckoned a disgrace for men to have long hair. Historical records bear, that in all countries in ancient times, that is, in the first ages, men wore long hair. Hence also the poets, in speaking of the ancients, are accustomed to apply to them the common epithet of unshorn. It was not until a late period that barbers began to be employed at Rome -- about the time of Africanus the elder. And at the time when Paul wrote these things, the practice of having the hair shorn had not yet come into use in the provinces of Gaul or in Germany. Nay more, it would have been reckoned an unseemly thing for men, no less than for women, to be shorn or shaven; but as in Greece it was reckoned all unbecoming thing for a man to allow his hair to grow long, so that those who did so were remarked as effeminate, he reckons as nature a custom that had come to be confirmed.
16. But if any man seem
. A contentious person is one whose humor inclines him to stir up disputes, and does not care what becomes of the truth. Of this description are all who, without any necessity, abolish good and useful customs -- raise disputes respecting matters that are not doubtful -- who do not yield to reasonings -- who cannot endure that any one should be above them. Of this description, also, are those (ajkoinw>nhtoi) would be singular persons who, from a foolish affectation, aim at some new and unusual way of acting. Such persons Paul does not reckon worthy of being replied to, inasmuch as contention is a pernicious thing, and ought, therefore, to be banished from the Churches. By this he teaches us, that those that are obstinate and fond of quarrelling, should rather be restrained by authority than confuted by lengthened disputations. For you will never have an end of contentions, if you are disposed to contend with a combative person until you have vanquished him; for though vanquished a hundred times, he would argue still. Let us therefore carefully mark this passage, that we may not allow ourselves to be carried away with needless disputations, provided at the same time we know how to distinguish contentious persons. For we must not always reckon as contentious the man who does not acquiesce in our decisions, or who ventures to contradict us; but when temper and obstinacy show themselves, let us then say with Paul, that contentions are at variance with the custom of the Church.