You stated that the law is proof of bigotry, well at first glance it sounds that way, but lets look at the law in more depth to see if it's really bigoted or if it actually protects the religious rights of Protestants and Catholics. When the Orange Order made that law that an Orangeman can't marry a Roman Catholic, the Roman Catholic church already had a law in place that the children of mixed marriages had to be brought up Roman Catholic. This rule encouraged the ethnic cleansing of the 'other' religion. In the Rep of Ireland it virtually wiped out Protestantism, decreased it from 10% in the 1900's to 3% in the 1980's. This law meant that the Parent who wasn't Roman Catholic could not teach their own children their own religion, the children whom you helped bring into the world were not allowed to learn the faith of the 'other' parent because of a Roman Catholic law. One could say that this law was like a form of religious punishment for the spouse who wasn't Roman Catholic. The nature of this law means that one religion has to suffer over and above the other, It's a law which wipes out and destroys other religions.
Now compare that RC law to the Orange Order law, where they don't encourage mixed marriages, are they actually guilty of this bigotry John? Have they created a law which is as damaging to another religion than the law created by the Roman Catholics? You'll find that this law of the Orange Order actually prevents one religion from gaining over another and leaves the demographics of religion down to God.
Makes you wonder why God commanded us, "Be ye not unequally yoked together" It would seem God's law is the best, he knows the pitfalls of mixed marriage, he knows that one religion will set rules up which undermine the other, ultimately undermining his Godly plan.