Sorry, but Marriage is civil AND religious construct. The Church is only concerned about the religious. Marriages outside the Catholic Church ARE NOT considered religious marriages BY THE CHURCH of ROME.
I am afraid you are overstating the situation. The Catholic Church does in fact recognize the marriages of Protestants and other Christians, and this is exactly why annulments are sought by people coming into the Church. If such marriages were not seen as binding by the Church there would be no problem at all, but they are and so must be addressed when there have been divorces and remarriages. The only such marriages which the Church doesn't recognize are those which actually have been annulled, so to speak, and this was because they lacked something in matter or form, not because they were performed outside of the Church.
I do not excuse Gingrich for being a bad husband, we are all lacking in perfection. Yet to hear some talk , you would think he strangled his former wives and buried them in the back yard.