Dolphins aren't people. Period. We don't eat people because that is cannibalism, illegal, and they are people. Animals aren't people. People are better than animals. Evolution.
.. Referring to later in the post do you honestly think they are 'higher' life forms than us because they don't ruin their environment and have wars? ...If so, and given the chance between a dolphin being killed and a human being killed you would choose the human..? That's pretty messed up.
You say you are studying to be a vet but if you truly think that "people are better than animals" I think you missed something in basic biology because people ARE animals, unless you would rather class us as a species of plant, or perhaps we aren't even a eukaryote organism.
So we have gone a long way to destroying the only known planet that can support us in order to build upon a society based around such a foolish concept as a monetary economy. I fail to see how sky scrapers and hydrogen bombs make us better.
Cannibalism is a widely practice trait in nature and was an acceptable practice in many human cultures until forceful inclusion of certain religious moral values upon these cultures. Your argument of its illegality is illegitimate. You state that the Japanese fishermen have been killing dolphins for years as justification for the continuation of the practice. By that logic cannibalistic cultures should be allowed to continue and thrive for as long as it is environmentally sustainable to eat human beings (I imagine a fairly long time if cannibal groups remain relatively small and select.)