But you beat me to it.
A Civil Union being seen equivalent to a Marriage... that means a Marriage *IS* a Civil Union... but a Civil Union is not necessarily a Marriage and can be separated out from that. As soon as they are asking if the two in the Union are Male/Male, Male/Female, Female/Female... they are necessarily leaving out transgendered or eunics and are going to be marking the License as a Union and not a Marriage. The form doesn't need to ask for the sake of the Marriage.
Again, Separate but Equal was tried in Segregation days (and still is) and it is/was a horrible flop and failure. Insurance companies from Auto-Home-Life-Health types will deselect based on that status. Even if it is illegal... What stops them now from doing illegal things... nothing.
Its not just Insurance. Its everything being geared towards a Man and Woman being married, everything. Things you wouldn't normally think about kinds of things. Like being allowed into a "couples" (non-religious) retreat. Or perhaps things as simple as Airlines seating Married Couples priority seating. Honeymoon planning... think of just how many Resorts are setup for Man/Woman couples. Think of the impact a "Civil Union" would have on those kinds of things.
What about the requirements for Married Couples to be able to adopt Children... Same Sex "civil-union" couples are being denied the ability to do that. Where as Single Parents aren't, what?
It goes much further... Marriage is ingrained into people as something special. Civil Union just doesn't cut it with me. It won't be enough for Governmental Agencies (Federal or other wise). It won't be enough for Insurance companies. It won't be enough for places like Hobby Lobby, I'd argue that Hobby Lobby would deselect Employment based on the fact.
Think about a Gay or Lesbian Cop, being a member of a Civil Union, being "Killed in the Line of Duty"... Do you actually think the Police organization would do a payout to widow(er) Civil Union member? the Union would fight for it, but in the end more than likely "Legally Married" is probably in the wording of the contracts... it means legally *NO Payout*. Just one example where this is serious.
Sorry, it is about the Redefinition of the term Marriage. It means more because its been given more. Civil Union just doesn't cut it.