Homosexuality is not a civil rights issue it is a morality isssue and until you can emirically prove that homosexuality is innate, immutable, and unchangeable you don't have a leg to stand on based on civil rights.
As to your statement denying that gays are more proiscuous than straights that is simply ludicrous as even the Advocate has published articles that dispute your claim. Also the Advocate and other gay journals have published articles on the transitory nature of gay relationships. You need to do your own research before you make statements you can't backup.
Your example involving married vs. unmarried couples does not apply to this discussion unless you include unmarried heterosexuals. As to cities that have adopted partner benefits for unmarried heterosexuals you could make a good case in any Federal court that disallowing benefits for gay couples violates the 14th Ammendment. So, again you are getting paranoid over what might happen. As to employee benefits Kansas law cannot force a New York based corporation to alter their benefit package and if Kansas tried Kansas could loose some large employers. You are being short sighted.
Leviticus is only part of what the Bible teaches concerning homosexuality. There are passages in Romans, 1 Corinthians, and 1 Timothy as well as a plethora of passages dealing with fornication.
As to the divorce rate among heterosexuals what does that have to do with this discussion. I am well aware of the stats on divorce and until Christians clean up their own house they don't have much room to criticize non-Christians.