If same sex marriage becomes legal, what right do we have to deny people who want to marry 3 women, or someone who wants to marry a sheep? None.

The reason we have Biblical standards for life is not to prevent us from doing what we really want to do, it's to protect us from undesirable consequences. The secular world sees these standards as a roadblock to their freedom. We see the standards as protection. Just look at the results of trends that took deep root in the 60s and tell me that God's standards aren't better for a society.