I would respond that these issues: abortion (like murder) and gay marriage are issues that belong to the states, which through most of history owned them. Demanding that the federal government resolve these issues through federal power (contrary to the constitution's clear meaning) just opens a Pandora's box and kills the principled arguments against liberal social engineering at the federal level.
Terri Shivo case was another example where most Americans agreed that the federal government was far overreaching it's authority for political purposes. (Looked clearly unconstitutional.)
For every one of these issues there are political arguments on both side but a federal solution always takes away our freedom to ‘walk with our feet’.
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