Abortion and Slavery

In response to Michael S.'s question, I don't mean that  the comparison is extreme in the sense that it is outside the mainstream of political discourse, since I take it that it is the view of a fairly large number of people.  Nor do I mean it is extreme if one accepts the view of abortion as morally the same as murder or infanticide.  I suppose I view it as extreme because it is intended to rule out as unreasonable any discussion of possibility that the legality of abortion might be tolerable on prudential grounds.  I take it as a given that no one within the political mainstream would entertain the same with respect to slavery.  In fact, I think most people would say that any system that recognized legal slavery would be unworthy of obedience and would justify active (even violent) resistance on a broad range of fronts.  Accordingly, the comparison of abortion to slavery seems to me to be extreme in its implications and, consequently, to open those who espouse it to Rauch's criticism that they do not seem willing to follow their own principles to their logical conclusions, just as does the comparison of abortion to murder.  I guess I take issue with (and would characterize as "extreme") modes of argument about abortion that trade, implicitly or explicitly, on the plausibility given to them by a comparison with murder when almost none of the people making these arguments actually behave as if abortion were really "murder" in any sense in which that word is normally used.