Brand-name clothes is not really a commodity, and there is nothing efficient about destroying inventory (at scale, destroying small returns might be efficient). The brand name is a psychological trick that transforms commodity items into premium products, and supply control (destruction) seeks to gatekeep the brand and maintain that image. It works because the cost of the textiles is a small fraction of their retail price. It wouldn't work for example for things that cost more to produce, like electronics, which is why those are usually sold refurbished.

Supply control usually benefits the producers, despite what it may seem (destroying items). Increasing the supply lowers the relative pricing power of the vendors, and reduces the price an average consumer pays for the same item, even if the retail price for the item technically increases.

I'd say it is good in the long run. If people spent less on clothes, they'd have more to spend on other goods and services or invest in productive endeavors.