Even if the impact is so close to "zero" that it is not measurable, it is still in no way acceptable that for every fish in a tank at the pet store there are 9 others that died.
When does the love of the hobby start to eclipse the love of the subject?
Take fish out of the wild? You bet! but responsibly and then the goal should be breed them in captivity.
The thing is that there are
captive breeding efforts in the marine hobby. It takes a lot more effort to raise Marine Fish (especially ones that have pelagic larvae stages) and people have recently been cracking very tough fish. Most people that don't have enough knowledge to keep a SW tank normally go with Clownfish anyways, which are breed extensively in the U.S.
Show me sufficient evidence of extensive use of harmful methods of collection. Even live-rock is being man-made and aqua-cultured.