Better World Shopper is an interesting site. I can't comment at all regarding the quality or validity of their research methodology, but their conclusions are certainly worthy of consideration.
And I think it's about time that we all come to grips with the understanding that there's nothing inferior, or particularly sinister or distasteful, about used clothing. For one thing, it's not like the clothing you buy at retail is particularly pristine, unworn or sanitary. Anybody who's ever worked in retail can tell horror stories about what is done to clothing before it's purchased and leaves the store as a "new" garment.
Secondly, I suspect that each and every one of us has access to laundry facilities and/or a dry cleaner. No matter what a garment might have been through before you purchase it, you can restore that item to a state probably cleaner than it was at the time of manufacture.
Of course, clothing does NOT have a memory. No conscious presence at all. It carries no karma, no good luck, or bad luck, or any other kind of sensibility. Clothing is an inanimate tool that we need for decency and protection, and we like for our personal adornment, and the pleasure it can bring to us.
Lastly, let's de-stigmatized this whole "second-hand" business once and for all. You wouldn't scorn someone for owning antiques. We need to expand that range of thinking to all kinds of items. ANYTHING that still has utility and wear in it should be allowed to be used, and worn, and enjoyed, until it's worn out. If it takes more than 1 person to wear out a garment, then so be it.
Let's quit being snobs about this, shall we?