Clearly, if you are opposed to abortion, you must also think this murder.
Not necessarily, though probably true in the general case. An embryo created as a clone may or may not have a soul according to a number of traditional modes of religious thought. As such, destroying it (a thing that might be considered an abomination against nature in the first place), wouldn't be murder at all.
Again, I think this is a minority position, but worth considering.
This is a far cry from questions about federal funding for stem cell research. In this case human embryos were created for the purpose of research, and were subsequently destroyed.
It is different, but how different depends a great deal on how you place value upon embryonic "life" and your view of cloning itself.
To wit, if a clone is a copy of you, what rights do you have over it? This is a topic that's been addressed in fiction and non-fiction alike, and your take on the matter might well affect your attitude towards the research in question.
More fundamental, however, is the other factor: the value of an embryo. I used to be of the mind that abortion is more or less the destruction of life, and therefore to be avoided.
[ Quick aside on my abortion stance in general : I have always felt it was an ethical matter that affects no one but the involved parties, and therefore not the sort of thing that ought to be legislated. There is little or no *societal* cost, even if you believe it to be unethical. Also, as unwanted pregnancies affect women so disproportionately that my opinions matter only insofar as I can say them and leave it at that. Even in a situation where I was the proximate cause of an unwanted pregnancy, I pretty much think my responsibility is to provide my argument, followed by support for her choice in the matter, whatever it is. Going further, I think that for the most part unwanted children carry a far, FAR higher societal cost than abortion; I don't at all believe in establishing a family that is statistically bound to suffer as a result.]
At any rate, my opinion has changed somewhat. Frankly, I'm more interested in protecting humans with thoughts, dreams, loves, ideas, etc. than I am in protecting proto-humans without those things. A young soldier in Iraq, or even a middle aged worker, deserves a hell of a lot more than a mass of newly differentiated cells, even if those cells have a heart that beats. Thus, to the extent that the loss of an embryo can teach us something about how to save or enrich the lives of actual, complete humans, I find it to be acceptable.
This shouldn't be read as complete disregard. I don't think embryos ought to be created and destroyed wontonly any more than I think we should hunt purely for entertainment, or slaughter animals we don't intend to use for food or other uses. At some point an embryo ought to begin getting more protection, commensurate with it's degree of development. Blastocysts aren't at that point. I agree that the definition of what that point is is quite difficult, but I think we should probably start by discussing when brain function (not brain development) kicks in. When do neurons start firing in a way that is similar to human cogitation or dreaming? Probably, the point is somewhere in that vicinity.
Now, cloning is another situation, and I do think a serious discussion needs to take place there. For myself, much as I view human life as being more or less defined by the learning and reasoning and, well, living, that we do after being born, I view clones as distinct beings, regardless of genetic provenance. We are not our DNA, so should we ever progress to the point of birthing a human clone, I will consider it to be a fully distinct and individual human like any other, and subject to no form of control by it's genetic donor.