If I'm wrong, tell us which arguments for protecting the one man and one woman definition of marriage is rational."
Could be because there is no rational reason. You have posted many inane reasons... all of which have been shown to be false or moot. There is absolutely no reason why two u.s. citizens of the same sex should not be allowed to enter into the civil contrract of marriage and enjoy all the benifits there of.
No one can demonstrate a compelling and legitimate governmental interest for refusing to treat same sex couples equally to opposite sex couples under the law. The excuses rely on irrational assertions, empty bumper sticker slogans like "protecting marriage", fear mongering, and inappropriate use of terminology.