Matthew Yglesias may be right about the opposition of Roman Catholic bishops and the Southern Baptist Convention to federal funding (not the legality, mind you) for contraception (his words here):
Their revealed behavior indicates that they don’t actually find abortion especially problematic, but just place it on a spectrum containing a general aversion to women controlling their own sexuality.
Nevertheless, his remarks form an implicit ad hominem argument against the position that ‘abortion’ (better known, in my judgement, as prenatal infanticide) is murder. [Note: Ad hominem argument is claiming that an argument’s wrong because the person arguing it is a bad person. One example is to argue that something is wrong because Hitler thought it. The problem with this is that not everything Hitler ever thought was wrong: I’m positive he would have agreed that he had ten fingers.]
For his point, that seeking common ground with opponents of ‘abortion’ merely exposes an extreme view but does not proceed beyond that policy-wise, this may be relevant. If, however, Mr Iglesias is using this to cast doubt on the integrity of the very proposition that premeditated induced ‘abortion’ is murder, this logical fallacy ought to be exposed.
I do wonder, though: does a postmodernist epistemology, which assumes that a truth claim is a power claim, lend itself to ad hominem style of argumentation?