Spear fishing done properly is a legal sport and ethical way of harvesting fish. People should be able to participate in their sports without suffering the prejudices of narrow minded people. All sports benefit from teaching and learning. A novice diver might do damage to the coral before he learns proper buoyancy control. That doesn’t mean diving is a bad sport.
Elbert, keep your prejudices on your boat and don’t call people derogatory names who are enjoying their sports.
And Rykat, I must disagree with your suggestion. Becoming proficient with a hawaiian sling is much more difficult than spearing with a spear gun. The objective should be to get the fish you want to eat in the most efficient manner. If a person can do that easier with a spear gun, then he should use that method. If you shoot at a fish, you want the best chance to get it and not just injure it.