The researchers argue that their work shows it is morally unacceptable...
See, this is what we get when we confuse science and activism. Should a "researcher" have any more weight with the public about what they consider "morally acceptable"?
I think there is some meat to this story: we need a more nuanced scale of what is morally acceptable or not that includes various forms of intelligence (without the same logic being used to treat disabled people poorly) I can't emphasize enough how important these issues are. Dolphins are obviously highly intelligent creatures. But such a discussion needs to happen from a neutral and reasonable standpoint. Asking folks who are deeply in love with their subject to tell us what's morally acceptable or not is whacked.
Doctors shouldn't treat themselves, lawyers shouldn't have themselves as clients, accountants shouldn't audit their own books, programmers shouldn't peer-review their own code -- and scientists shouldn't advocate on the topics they are deeply attached to. This is just common sense.
EDIT: Just to be clear, there are at least three problems with scientists-as-activist.
1) The public gets to make the decision on these issues. This means that any communication from scientists has to have as its goal informing the public, not persuading it. In an article like this, it is not clear to the public where the discussion of science ends and where the discussion of advocacy begins. This confusion, aside from being unethical in any profession, is a poor use of the public's resources.
2) The end result of such advocacy has a direct impact on the scientist's lives, creating a moral hazard. This is like when your chiropractor tells you that you have a bad back -- and need many more chiropractor visits. Maybe true, maybe not, but when a professional judgment can also be self-serving it creates mixed incentives and doubt, which is bad for any group of professionals
3) Morality is not science: you cannot add one and one and get "moral" or "immoral". When a conclusion like this is put forth by a scientist, it glosses over all sorts of other questions which other professionals are interested in, like when life begins, or what constitutes sentience. To make a statement about morality is -- at the very least -- to jump into areas for which you are not trained. As a professional, once again, it's your job to make it clear which things you speak about are part of your work and part of your opinions. The most important thing a scientist can say is "I don't know"
That's not even getting into the entire issue of just being too close to something to make a good call. Or -- if you think such behavior is okay -- the use of scientists as pawns to have proxy battles over other larger political causes.
These are not new standards. Other professions have been living inside of them for years. Ask your accounting consulting firm whether it's moral for you to invest in Indonesia and you'll get a very careful reply which will boil down to "I am not the person to ask that question of"