Imagine 150 years, if the world in it’s “enlightened” state in 2163 universally accepts that gay marriage is the right and proper rule, there is simply no controversy at all. Let's pretend it is 2163 and that the faiths handle their historical problems the way they do today.
Protestants -- True Christianity defense It is blatantly obvious to all that the bible perspicuously teaches that homosexual marriage is godly. It is a pity that in 2013 man's fallen state and sin led them to misread the bible and be opposed to homosexual marriage; worse yet that they tried to justify their sin on what they claimed were biblical grounds. It is wonderful gift of the grace of God that we have been given scriptures to correct such sinful doctrines, which just proves ecclesia semper reformanda.
Catholics -- Development of doctrine The magisterium of Christ's church has always taught that homosexual marriage is a godly sacrament and a Christian duty. There were debates in the 20th and 21st century on this topic, bishops on the other side of the issue. It may even have been the case they were the majority, but God infallibly guides his holy church. His Eminence's 2158 encyclical has made homosexual marriage a matter of personal conscience so as not to cause schism with those remaining traditionalists. Bishops from all over the world are currently compiling historical information about their diocese's historical pronouncements on the issue. After these are compiled national cardinals will gather the bishops into conferences to create a consolidated national report. These reports will be sent to the vatican for further study.... and finally in the 2318 encyclical attitudes towards homosexual marriage are no longer a matter of personal conscience
Fundamentalists (a) -- historical denial True Christians never believed homosexual marriage is ungodly, they can read the bible as clearly as I can. Teachings like this are spread by ungodly secularists to discredit the Christian faith.
Fundamentalist (b) -- holding fast Homosexual marriage is sinful and a denial of God's intent for marriage as expressed in Genesis. Anyone can clearly see that by reading scripture, the convoluted interpretations that are popular today are nothing more than justifications for sin.
Liberal Protestant -- Progressive revelation Our churches were leaders on the move towards homosexual marriage and this is something we are justifiable proud of. While scripture itself is murky the direction of scripture is perspicuous and along with the Holy Spirit has led our church to help rectify many past wrongs.
Jews -- restricted understanding It is important not to confuse a marriage between homosexuals and "Homosexual marriage". Homosexual marriage is still banned as sinful. However, a proper understanding of Rabbinic law on the issue has led towards us assembling the 23 criteria that were present in homosexual marriages in the 21st century. Modern marriages between homosexuals do not fulfill criteria 5 and 16. For example #5 marriage at that time was a state contract recognized between states while today it is international and state recognition is automatic; since no act of recognition takes place no marriage in the 21st century sense is taking place today between homosexuals.
LDS (a) -- implicit denial The church simply revises manuals dealing with marital doctrine to fully embrace homosexual marriage with quotes from the bible and the Book of Mormon. Mormons who jack into the information matrix can get brain dumps from anti-Mormon sites and see a full history of revisions to this doctrine, which somehow is supposed to be a justification for Protestantism. Mormon apologists argue that the church's stand on prop 8, even though it was directly funded by the church was never official doctrine.