I find this line of thought extremely tedious. We have never improved as a society by lining up all of our concerns in a nicely organized list by priority, and then tackling everything on the agenda sequentially.
I am reminded of people who scoff at giving money to bums on the grounds that it is an inefficient form of charity. In most cases, here is what happens:
1. Bum asks X for spare change.
2. X thinks "That's not an efficient way to give. I would be better off donating the couple bucks in my pocket to a charity that I have researched carefully."
3. "Sorry I don't have anything on me."
4. X goes and spends the money on a cup of coffee and completely forgets about the incident.
Now, obviously that's not what always happens. But it's what usually happens, and it's ridiculous. I've had people tell me that instead of giving money to homeless people, I should go buy fast food and hand it out. Of course, when asked if they have ever done this themselves, the answer is invariably "no". It's so easy to do nothing instead of something if you can convince yourself that the something is not the absolute ideal.
Finally, affording dolphins human rights is not in conflict with affording humans human rights. We will not delay the process of preventing human rights abuses by also preventing the abuse of dolphins. To ask the question "How can we think about giving dolphins basic rights when so many humans don't have basic rights?" may feel righteous, but it certainly doesn't actually do anything to help either cause. All it does is to reassure yourself that you don't need to worry about the dolphin situation.
I agree with the point you're making - we can address more than one problem at once - but I'm not sure the charity example is the best one.
People have a kind of mental 'karma quota', where once they've done so much good deeds, they don't feel a need to do more. It's a problem for environmental awareness, because people get daft advice like 'unplug your phone charger' (which achieves almost nothing), and then feel they've done their bit.
So the person walking past a homeless man probably won't go and give the same money to charity (hands up, I've done that). But the accumulated guilt might eventually make them go and donate money to something.
So there are actually some countervailing forces at work here. On the one hand, people who have social status associated with ethical behavior tend to be more likely to act unethically (I wish I could find a reference for that offhand, but no matter).
On the other hand, self-image plays a pretty big role in determining behavior. Robert Cialdini discusses this at length in Influence: Science and Practice. He discusses several studies that demonstrate that getting someone to take an action that affects their self-image makes them more likely to make decisions corresponding to that self-image in the future.
For example, researchers divided home owners into two groups. Those in Group A were initially approached and asked to place three-inch signs in their yards saying "be a safe driver", and most of them complied. Group B was not approached initially.
A few weeks after that, the researchers went back to everyone in both groups and asked them if they would be willing to place a large billboard in their yard saying "drive carefully". They were shown a picture example showing a poorly designed billboard so large that it almost entirely obscured the view of the house. Almost everyone in Group B declined. The majority in Group A accepted.
The conclusion of this, and many other experiments is fascinating: people have a powerful drive to behave consistently. We are strongly repulsed by the possibility of hypocrisy. So if you change someone's view of themselves to fit a certain pattern, they will tend to continue to conform to that pattern in the future. So to some degree at least, giving money to a homeless person will create in you an internal psychological pressure to be more altruistic in the future.
And choosing not to give money because you think giving it to charity would be more effective may inadvertently cause you to incorporate "cautious about donating" into your self-image, and cause you to have more difficulty with future altruism. After all, what if you gave money to the Red Cross instead of the homeless person, and then found out that they weren't such a great charity after all? You'd look like a hypocrite for being cautious with the bum, but not with the Red Cross. Your brain is very good at anticipating "I'll look like a hypocrite" and avoiding it, even when the end result is worse for everyone.
Incidentally, if you find this stuff fascinating (or terrifying), I highly recommend Cialdini's book. But it might make you a little paranoid about salespeople and marketers.
Our first, yes, but not our only. Otherwise, dolphins and whales might be extinct soon. There's nothing preventing you from supporting both, say, Amnesty International and Sea Sheperd, or Médecins Sans Frontières and Greenpeace - or all of them. This is not a binary decision.
But first we need to find out exactly which slaves have it the worst, and free all of them. We can't go around doing good things for anyone other than the absolute worst off people. Luckily this means we can spend all our time debating who has it worst instead of doing anything to help anyone.
This is snarcky but it points out as strongly as possible what is so wrong with prioritization of good causes, it should pop out automatically every time someone tries to discuss this. And I would like to add that there are enougth amount of humans for caring about all the good causes.
I suspect that "We" have agreed. That doesn't mean everyone has. It is unlikely that everyone will, unless of course we exclude some people from our definition of everyone. Shirley, this is not your intent.
Philosophically, placing human rights first is inherently inconsistent with the foundation of extending "equal" rights to other species.