This is the more compelling argument for gay marriage ever.
Actually, in my experience the argument usually goes like this:
"It's unnatural."
"It's found throughout nature."
"It's just a new liberal trend."
"It's been part of society, with varying degrees of acceptance, since the beginning of recorded history."
"It will take away my rights."
"It has nothing to do with your rights, your rights will stay the same."
"It will destroy the sanctity of marriage."
"A divorce rate of over 50% has already done that."
"It won't work because marriage is about procreation and gay couples can't have kids."
"Neither can many straight couples but we still let them marry."
"The kids that they do have will be messed up for life without a mother and father."
"Not according to every study ever done on the subject."
"It violates the holy book that I subscribe to."
"That book contains numerous inconsistencies and a wide variety of other rules that are considered outdated."
"It makes me feel icky."
"Aaaaand there it is."