Actually, all guides don't behave that way. In some places, like Saipan, you are required to go with a local guide if you don't live there. In others, I feel it's best for one of slight experience such as myself to go with someone who knows the waters. This is especially true when I'm on vacation. I generally don't dive twice with guides who molest sealife or shops who's entire dive staff does so.
As far as fish huggers are concerned, I treat the ocean as any natural place. I don't like people who molest squirrels in the forest, or shoot birds out of the sky (that they aren't going to eat). I love and respect nature, but am not about to chain myself to a redwood, etc. Still, at the rate humans are destroying the natural world, both above and below the waves, I think it's the least one could do to respect and try to preserve the environment by minimizing one's impact on it. Those who act otherwise are, in my opinion, selfish. They don't respect nature and they don't respect others who come after; whose experience will be diminished. Despite what some may believe or teach, nature was not put here for humanity's use, we are a part of nature.