It may be an exaggeration to say that used clothing is the only environmentally ethical answer, but it's certainly an option worth considering.
Even if they're largely sarcastic, the arguments here are specious. Used clothing is a great option, and it's unfortunate this column didn't mention it. As for these specific points:
1. "if everyone suddenly wanted "used" clothing, and shunned "new", the supply of "used" clothing would be expended in no time at all." It's highly unlikely that everyone would suddenly start shunning new clothing. And even if they did, they still might want to clear their closets of rarely worn items (perhaps to make room for new-to-them items). Clothing will obviously wear out and there will always been a need for a certain amount of new clothing, but the nice thing about supply and demand is that it's self-regulating.
2. "If you go to a department store to buy a new pair of pants, you are almost certain to find exactly the size, color, style you need/want on one trip." The majority of people who shop for used clothing know from experience that you can't walk into a thrift shop with a specific style and color of pants in mind. To do so is simply an exercise in frustration. The key to buying used is being flexible and working with what's available. (Having a sewing machine or knowing a good tailor is a big help.)
3. "A search for "used" clothing could be quite a journey, expending a great deal of fuel and time in the effort." Anyone who is shopping for used clothing for environmental reasons is surely already aware of the effect that gas consumption has on the environment. Luckily, even if the buyer isn't flexible about what they're looking for, in many large cities thrift stores are clustered in a particular area and it's possible to make one trip to visit multiple stores. It's also possible to take public transportation and go to a thrift store on the way to another destination to reduce this kind of impact.
4. "would it then be unethical to bury dead people with their clothes on." Allow me to take you seriously here. Of course it makes no logical sense to bury someone in clothing (which is a long way from suggesting it's unethical). Burial rituals are fraught with cultural significance (and taboo), but it is never a bad thing to consciously consider these rituals rather than blindly following them, even if you ultimately decide that, yes, you and your loved ones will be dressed. (I'm not advocating this for open caskets, though!) Many people are reconsidering other aspects of burial ritual (such as the impact of embalming and elaborate coffins), a decision about clothing can be thrown into the mix. I'm considering being buried in Greensprings natural cemetery (<link>), possibly with a tree as my only marker, possibly naked. :)
5. "When does the "ick" factor kick in." Typically, most of a deceased person's clothing is donated to a second-hand outlet of some kind. I'm not sure why there's an ick factor; any reputable second hand shop will wash all clothing before putting it out for sale. If the idea of wearing clothing that previously belonged to a dead person is repulsive, then used clothing is probably not for you (which is fine). I personally wear and cherish several outfits that belonged to my mother (who died when I was 7).
6. "If there is such a thing as the "most" environmentally ethical answer, then it is to buy the clothing that you actually need, and wear it till you got the optimum amount of use of it." Now this I can agree with wholeheartedly! Clothing can be sewn or patched or even tailored into something else, even if that something is then only suitable for gardening, painting or car repair. After that, cotton rags work as well as or better than paper towels in many cases.
7. "Of course, very few people think like this, and it is not how the fashion/clothing industry works." We didn't get into the environmental mess we're in by thinking-- we got here by not thinking. Discussing things that we normally do without thinking empowers us all make positive, responsible choices. As for the fashion industry (and our entire, deeply-flawed, consumer-driven economy)... well, all of us can use a some improvement.
8. "What people wear is almost as a much a statement about ones self image, as it is about protecting ourselves against the elements, perhaps more so." But buying and wearing used is a statement, and I would argue that it's a much more powerful one than having the latest and greatest in trendy clothing.