The real problem with the phrase in the title isn't even that it's moronic, but that it's oxymoronic. The Renaissance is a period which, broadly and loosely speaking, extended from the 14th through the 16th centuries (but see this node). This period saw the perfection of armor; all-plate armor was not even invented until the 15th century. Here, for instance, is a sketch of the armor of Jean Parisot de la Valette, Grand Master of the Hospitallers of St. John of Malta, in which he fought the Turk in 1565. Moreover, it is not at all as though armor went out of use in the early modern period; this is the parade armor of the later grand master Alof de Wignacourt, who held that position from 1601 to 1622, and here is the armor of a Napoleonic cuirassier, that is, from the 19th century.
Lastly, this is a picture of the hat and sword of Jean Parisot de la Valette. The sword is smack dab in the transition from sidesword to rapier. It's still an example of the former; but it could be used according to the principles of Agrippa without difficulty. It and the sword were votive gifts from the grandmaster to God, after he had successfully repelled the Ottoman siege; so, although it is a clear example of what we would consider a dress sword, it seems clear that he thought it adequate to wear, with his armor, in one of the largest military engagements of that century. In the same way, the fact that he wore the armor goes to show that he thought it good to protect against such swords, and would hardly be »stuck full of holes« in spite of it. The entire distinction being made is rot; it is the product of a sort of ignorance which only 1970s Californians, in all of history, seem to have been capable of.
Rather, the dichotomy the original noder seems to have noticed and be fumbling for the explanation to is that between military and civilian. It is very much true that a man would not often wear armor in civilian life, because that would have been like doing your shopping in a ghillie suit and with an assault rifle over your shoulder, and most people are not that stupid; but the same fellows who wore the armor in war were highly overrepresented among the wearers of dress swords in peace. Rolling up to one of them and calling him a ponce for having a basic grasp of social codes would, to continue the analogy, have been about as advisable as informing a modern Russian soldier that he's »a weak pansy without his guns handy«: if you're very lucky, he will be a temperate man, find you amusing, and only laugh at you or fuck with you a little bit; but if not, you will learn new and fascinating nuances to the phrase »in deep shit«.
I can't in good conscience recommend it, even for science.