Hey Daz, welcome to Seabreeze!
Nothing wrong with spearfishing (and I consider myself an environmentalist, but a realist type, not a treehugging type).
Great way to catch a meal.
But like anything, some spearfishers go too far and do stupid things like take a huge amount of the population of certain tasty/pricey species that ruins things for everyone (other spearfishers have no chance, us environmentalists not happy, the ecosystem loose a link>less other species for you to catch, etc, pro-fishermen loose income, etc.)
So enjoy your spearfishing, drop the 'I hate environmentalists' attitude (one side not understanding the other, and emotional not reasonable judgement clouds the real issue and then the greater good for both sides doesn't come out)
I.e: It doesn't allow you to catch fish and enjoy it or us our happiness in knowing there is biodiversity out there
So I encourage you to spearfish, but only take what you need, get your spearfishing mates to be reasonable about catchrates etc (not saying you aren't reasonable already, only you know, if you're informed enough) and mix it up (species and spots), to keep it sustainable.
We want you to be able to spearfish for as long as it makes you happy, not just intensly for a couple of years!
Cheers and happy spearfishing man (btw, been thinking of getting into handspearing from a non-spearing background, is this really hard but fun?)
Ps sorry for the rant, but I like to clear up misunderstandings for the greater good of the environment (now I sound like a hippy hehe

!)