It was not offered as a demonstration (i.e., proof) of such. It was offered as an illustration (i.e., example) of the failure of many people who vehemently insist upon a "right to choose" with respect to abortion (whether they do so upon "principled" grounds or not) to grant that right in numerous other respects. Such linquistic and conceptual hypocrisy indicates either a lack of principle or a limited (and politically expedient) application of principle in the form of semantic opportunism. And this observation seems to be especially applicable with respect to "pro-choice" (and generally liberal) Democrats (who were, after all, the specific antecedents of the "they" to whom you referred - and not just any "pro-choice people"). Not to mention the fact that DA was ironically - and perhaps facetiously - commenting upon an ostensible lack of political expediency in Democrats' support of abortion ...
Who said anything about defending "everything" having to do with choice? In order to demonstrate the infelicity (not to mention the hypocrisy) of using "pro-choice" as a self-adopted label, it is sufficient to show that there are some number of things having to do with choice that self-proclaimed "pro-choicers" not only do not defend, but actively reject. If those who call themselves "pro-choice" don't like such accusations of hypocrisy or lack of principle, then they should choose some other label for themselves ...
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