There are a lot of explanations of consequentialism and utilitarianism out there, but not a lot of persuasive essays trying to convert people. I would like to fill that gap with a pro-consequentialist FAQ. The target audience is people who are intelligent but may not have a strong philosophy background or have thought about this matter too much before (ie it's not intended to solve every single problem or be up to the usual standards of discussion on LW).
I have a draft up at http://www.raikoth.net/consequentialism.html (yes, I have since realized the background is horrible, and changing it is on my list of things to do). Feedback would be appreciated, especially from non-consequentialists and non-philosophers since they're the target audience.
There is more than one way to interpret your original objection and I wonder whether you and NihilCredo are talking about the same thing. Consider two situations: (1) The toddler and the pig are in mortal danger. You can save only one of them. (2) The toddler and the pig will both live long lives but they're about to experience extreme pain. Once again, you can prevent it for only one of them.
I think it's correct to take future states into consideration in the second case where we know that there will be some suffering in the future and we can minimize it by asking whether humans or pigs are more vulnerable to suffering resulting from past traumas.
But basing the decision of which being gets to have the descendants of its current mind-state realized in the future on the awesomeness of those descendants rather than solely on the current mind-state seems wrong. And the logical conclusion of that wouldn't be opposition to abortion, it would be opposition to anything that isn't efficient procreation.
Why throw away that information? Because it's about the future?