The damage to wild reefs is irrelevant, there are so many other issues destroying reefs that if aquariums contribute, they barely speed things up, they by no means cause the problem. One major issue is all the vacationers, resorts set right on the beach, hauling snorkelers out to to the reefs, etc. Another even bigger issue is our inland land management. We put crops right up to rivers that drain into the ocean, right on to reefs. There is no buffer zone. This means that all the run off, all the fertilizers, all the crap we put on the land dumps right on to the reef. These excess nutrients cause algae blooms that convert the reef in to an algae farm. They actually figured out that the runoff in Australia caused a bloom of a certain type of algae that larval crown of thorns feed on. This means their numbers went crazy, which meant they ate more corals and destroyed the reef. And it could all be avoided if we had 10 meters of untouched natural vegetation between our agricultural fields and the streams their run off dumps in to.
Global warming is another possible issue, hard to say how that will pan out long term, but it is a huge risk factor.
As far as real sources go you will have to google, check the references on wikipedia, but there are tons of facts out there about pollution, excessive nutrients, etc.
Very little is captive bred. More and more species are being bred every year, but it is a tough process. Even with the species that are bred, like clownfish, most are still wild caught.