We need to note that accepting same-sex marriages is not, in principle, a good thing, and I believe that many Europeans have this point of view. However, the European liberal and tolerant spirit states that, passing over any pros and cons, there should not exist, in principle, any authority to oppose to the wish of the people to search and experiment new ways of life together. European homosexuals are Europeans, and have the right to live their life as they consider it right.
Note: The fact that the Christian Church, created by Europeans for Europeans, has come at times into violent conflict with the European spirit, does not mean at all that it is a non-European Church. During the 2000 years of Christianity, the Christian Church had a very positive role in keeping the stability of the world, and gave hope to a lot of people. Leaving faith behind, created monsters (e.g. Communism). This section wants only to show to the Church, that it should be more flexible and, independent of its great merits, avoid to get into conflict with the European spirit. The European spirit has always been victorious and will always win any battle with the Christian spirit.
Let's follow however some facts. The first fundamental symbolic model is Euclid's geometry. It was created about the year 300 BC and is unmodified up to our days. The scolars of the period left us a huge amount of scientific data kept in large libraries of the Antiquity. At 415 AD, the Christian leaders destroyed the great library of Alexandria, because the books have been considered contrary to the Christian religion.
The result was that scientific knowledge has been completely destroyed for a very long time (the European civilization entered in the Dark Ages), so that the next fundamental symbolic model (Newton) appeared over 2000 years after Euclid! It is clear that the Christian Church had an active role in this unacceptable big delay, by the destruction of the books and blocking freethinking. However, it is not clear that this delay was caused by the emergence of the monotheist Christian religion or it is associated with a characteristic of the development of the brain. I mean, any monotheist religion wants the control of the thinking system of the people. The main problem is if the people accept this, or not. The Christian Church used to keep up to fifty years ago a list of forbidden books and ideas, but very few people take it in consideration. The general problem is still open.