As for dictators, they are violating international law. Abortion is legal in the US (withing certain parameters), and international law does not declare it to be illegal either.
International law primarily regards the interactions between nations rather than the actions within a nation. It is debatable whether or not a nation that is non-signatory to a treaty has violated a law when they fail to abide by its precepts.
I think most people would claim that murder is intrinsically wrong, and is not bad merely because it is contrary to some words on a piece of paper.
People can disagree as to what is unjustified; one person might consider a death in an arranged duel to be murder, while another might consider it justified. Under the law of today it is unlawful, under many laws 200 years ago it would be lawful.
Do they? They are the ones who define the law after all.
http://www.pewforum.org/fact-sheet/public-opinion-on-abortio...
70% of evangelicals are opposed, while 44% of Catholics are. From that you might conclude that since the majority of Catholics are not opposed to abortion that proves your case. That would be wrong. The church and those who oppose it are far more vocal and influential than those who support it.
Really, this topic is in the news all the time. I don't know how the religious connection has escaped you.
First, you use "murder" incorrectly. Abortion, in the US, is legal, and therefore not murder. Murder is defined as an illegal killing. That is why when someone is given the death penalty, they are said to be killed, not murdered. We say soldiers kill the enemy, not murder the enemy. By using "murder" you are adopting the conflation that anti-abortion activists have been (apparently) successful in promoting.
Second, nobody doubts that a zygote is alive. Nearly every cell in your body is alive (barring hair, nails, upper layers of skin, recently recycled cells), including sperm and eggs. When an egg and a sperm fuse, the result is also alive. The question is whether the rights of the zygote->blastula->fetus->baby trump the rights of the woman who is carrying it.
Obviously, by the time it becomes a baby, the baby's rights trump the desires of the woman carrying it, in general -- everybody agrees on that. Some people conceive (pun not intended) of the fertilized egg as being fully human, something God ordained and which is the vessel for a soul which has been waiting for that very zygote, and by aborting it, one is subverting God's will and destroying the intended future destiny of that soul.
Others don't share that belief. There is certainly no bright line dividing when that fetus is developed enough that its rights are superior to that of its mother, and deciding where to place that light should not be taken lightly and will cause discomfort. But we deal with such things all the time. It is legal to drive 45 MPH on the street near my house, but not 46. Yes it is somewhat arbitrary but not unreasonable either. That we have to make an uneasy boundary somewhere on the continuum isn't reason to declare that the speed limit should be zero, or that there should be no speed limit at all.
It should also be noted that at the time Roe v Wade was decided, Protestants and even evangelical Protestants by and large were not bothered by the decision. Catholics were, of course. It wasn't until the rise of the Moral Majority that the issue became objectionable to so many religious groups.