Since I was specifically mentioned, I guess I can throw in my two cents. Spearfishing is the most environmentally responsible means to take fish for human consumption. There is generally no bait, no lost nets, lost lines or hooks and very low by-catch or unintended or under-sized take. It is efficient and has minimal waste and unintended impact. Paddling off the beach with a kayak and freediving for your dinner, can and should be one of the most responsible means to harvest fish.
The benefits of spearfishing (over other methods of take) are however, contingent upon the diver utilizing responsible methods. This would encompass a wide range of practices which would include not targeting undersized fish or species which are out of season or fish species which fall under protected status.
Responsible practices also include being aware of the environment, not impacting coral etc. Divers often use sound to attract fish. This may include grunting, tapping and some diver even use mechanical clickers. Tapping or clicking on the reef structure is a valid method, but it should never be done on live coral. In almost all instances, there are portions of the reef which are "dead" or covered with algae and any tapping can be done on these areas.
Spearfisherman should be just as concerned about the health of our reefs as every other diver, perhaps even more so, since we are consumptive users.
Thanks
Dano