The term "traditional marriage" is a modern invention because there has been no such thing as a simple, codified form of marriage throughout history, religion and geography. Besides the examples given in the video, back in Biblical days traditional marriage meant marrying more than one wife. It also meant and still does in some parts of the world that women are chattel and basically auctioned off to the would be husband who has the most goats.
It meant in the medieval period to marry out of status and hope of improving that status rather than out of love. Yet love from another being is what we all yearn for and hope to achieve in this life. Even monks who don't marry express love for the Dharma and the Sangha as well as for the laity. Their marriage is again, not "traditional" but their marriage to the three jewels is no less important and fulfilling.
How twisted have some religious veins become that some people are using them to deny people basic happiness and love in a world that is so full of suffering. Why would we want to cause even more suffering by denying people the right to marry the person that they want to share their life with? Shouldn't we be applauding people who want to commit to honor and cherish each other in this world of hatred, isolation and division? Without love for each other I ask, "What chance do we have as a species?"
~Peace to all beings~