ComputerGuru's main point was showing how similar dolphins are to humans, in the way they live and socialize, and stating that, because of those reasons, killing them is wrong. Yes, they might be doing it for their own living, but that doesn't make it any less wrong. In the end, we all work for our food, or to cover our needs in general, but that does not justify the work of paid assassins for example, or any other job that directly threatens other humans' lives.
† I'm kind of in a cognitive dissonance state about killing animals for eating, as i do consider animals to be not different in essence to humans --i think that our difference are only quantitative instead of qualitative-- but at the same time i eat animal meat, so i'm contributing to their killing.