Marriage isn't about love, it's about building units for a sustainable society. It isn't about sex or religion and it isn't about perceived rights.
A Breadwinner + A Nurturer reproducing relatively balanced offspring to continue the society and the species. There are plenty of dysfunctional Heterosexuals that shouldn't reproduce either.
In history, all else has failed. Best you go argue with history.
History also says that minorities get persecuted when civilized society fails.
