There's nothing wrong with sticking up for animals, Wellard, and I don't think there is. But, PETA-Freaks switch their brains off when doing so. What about the guy they attacked for putting a wounded bird out of its misery? What about that mink farm they invaded where they freed all the minks only to have fully half of them kill each other on the way out and the other half released into an environment where they are an invasive species?? They give a good cause a bad name.
I don't think it's wrong to eat animals - it is our place in the food chain. And, what you consume (i.e. put into your body) is as personal a choice as who you sleep with - so I don't question those choices (except on the theoretical level) just like I don't question choices on religion (except on the theoretical level). My vegetarianism comes from a loathing of animal cruelty and food safety issues in FACTORY farming (note: the MAJOR source of our food).
I do not think it is wrong to ride a horse, either. Nor teach a dog to hunt (though some owners are cruel to their hunting dogs and that's a different situation). Similarly, I do not see it as wrong to teach Dolphins to help in this way. Now, I don't have statistics on dolphin-deaths-by-mines, and I can't speak completely to this issue without that information. But, I would bet these dolphins live in the lap of luxury. Dolphins don't cooperate very well when they aren't treated very well - they are simply too aware of their circumstances.
And, is a machine better? If the dolphin is treated as a partner and friend and treated well by its (I hate this word with animals) *owner*, then isn't it the best symbiosis? I mean we're talking cooperation here, not death-by-longlines. I know that my Ranger D&D PC would never give up his wolf for a mechanical contraption.