"the consequences of bringing a dangerous and destructive lifestyle into mainstream society."

What consequences... of doing what ? Do you believe that the health problems of the homosexual population will be better addressed if they are "quaranteened" from the "mainstream"? Do you believe that, if homosexuality is less stigmatized, more people will want to become homosexual, or try a little homosexual experience, thereby spreading HIV more widely? Do you believe that if homosexual males are no longer stigmatized your daughter may want to marry one?
How would allowing same sex marriage increase the danger to anyone's health, or any other aspect of their well being?