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Right, as your snippet points out, some prefer to say orca rather than killer whale, because they aren't whales, and the connotations of "killer" aren't so nice.
About the conference thing, let me rephrase it: as a native English speaker, it surprises me to hear someone call orcas dolphins. It is the first time in my 46 years I have heard that, and I do like animals quite a bit and actively read and watch documentaries about them
I know that "killer whale" is the more common name for native English speakers, and that is fine. According to some classification schemes dolphins are subspecies of whales. I am not a native English speaker and have been calling it a dolphin for at least 10 years. Or orca, more often. Or spekkhogger, since a couple of years.