Reading this marvelous book by Michael Burleigh reveals how deeply Catholicism has been openly woven through global politics over the past several hundred years, and how deeply the Church has suffered for that involvement.
The situation in the United States, where religion is openly not involved but surely expressed through the speechmaking of politicians, is built most clearly on the foundations of Christ’s gospel; that acceptance is always a matter of choice and to make it coercive, as has been done in so many countries (Catholic or not) is to lose that essence of free will.
As strongly pro life as I am, it would not be a matter of free will to pass a constitutional amendment banning abortion as that would make coercive the basic tenet of our faith, that each life is precious; while to the secular, virtually all life is expendable as it has no eternal value, only that given it by earthly powers.