I didn't care for the chart.
Gay marriage is another vivid case of separation of church from the state. Marriage itself carries a volley of legal ratifications and rights that simply cannot be obtained just by "living together for a long time" with someone. Marriage is an incredibly powerful social right that goes far beyond a simple symbolic ritual.
It's a consequence of religion being melded into the state. And religious sects, being the starfishs they are, continue to use this as a tool to try to dictate how people should be. It's barbaric theology which people need to stop sympathizing with.