Becomming a certified diver doesn't mean we automatically signed up for Greenpeace and the like. I for one, am fine with people spearfishing - it's not much different than fishing from a boat. I like the notion of skin diving to spear rather than using SCUBA, but I still have nothing against using SCUBA to get your fish. Spearfisherman are not eradicating entire species and completely destroying reefs. It's the big commerical giants that are doing the harm by dragging nets and cages over reefs.
That said, I have never spearfished, but am looking forward to spearing lionfish in Cozumel next week. I also kind of wish I bought a bigger spear... I wouldn't mind bagging me a nice dinner! I've also stopped eating octopus since becomming a diver. Nothing against people who do, it's just that I LOVE seeing octopus underwater - they're one of my favorites to see, so I have a hard time eating them now. Same with cuddlefish and flounder. I do however, LOVE eating crabs, shrimp, tuna, salmon, and lobster (real lobster - the ones with claws from the northeast). Although I was at a presnetation about shark conservation and research not too long ago, and the researcher said if there's one thing he will absolutely not eat anymore, is shrimp, because of how the harvesting of them just absolutely destroys the underwater world - so I will try to eat only farm raised shrimp from now on... but if I'm hungry and in the mood... no promises, yet.
I am a human, therefore I am a carnivore by nature.