What is human rights if not a legal issue? Humans determine human rights, and they (we) do it through legal systems. He twisted a straight-forward legal question into something metaphysical, which rendered it essentially unanswerable (IOW, he ducked it). Given the circumstances, it was a wise tack. There was little else he could do.
At present the "pro-life" political theory is aimed at directing the "pro-life" understanding with God brought to us by a group of Americans on this subject as the only valid conversation any American can have with God. And, this is political because this argument benefits some religious fanatic seeking political power. It does not benefit unborn Americans because if someone wants an abortion they will get one. It does not advance respect for life as illegal abortions are fraught with peril for the mother's life.
The "pro-choice" political theory seeks to depoliticize the relationship anyone has with their god, and leave this decision to that person. There is no political power to be had by depoliticizing the relationship anyone may have with their god.
So far what I see about religious priorities making their way into politics is not good. So, even without ever being likely to face a decision myself about abortion, I am pro-choice because it reduces the influence of nutball religious freaks. Let them exercise their influence on those who voluntarily come to them. I don't want them anywhere near any government decision making groups or individuals.
And the fact that Obama agrees may be perceived to be "dodging" the question. The fact is, the question is bullshit. If you sling bullshit at me, I, too, would be inclined to duck or dodge. Who wants to be hit by bullshit? Jim