Seems to me your rational argument applies to existing contracts, not contracts not entered into. So of course I'm confused why you think the Constitution's Contract Clause applies to future marriage contracts between two men or two women?
You simply seem to be unable to comprehend simple logic.
By legal definition, a marriage contract is specific to a man and a woman, such does not deny a same sex couple to contract the equivalent obligations between themselves, yet such is not by legal, historical, and traditional definition a marriage contract which requires the party's entering into it to be of the opposite sex to fulfill the definition of such.
You seem to be of the misunderstanding that unless the same sex contract is labeled by definition a marriage contract that the obligations therein are somehow being impaired.
Not at all.
You said, "it is impossible to impair a contractual obligation before that contract is made, however a State cannot diminish the obligations of that contract once it is entered into."
Meaning you admit the Constitution's contract clause offers no protection to marriage contracts for same-sex couples who have not yet entered into marriage. At least you finally admit that clause is irrelevant in terms of people who haven't gotten married yet. That's a start anyway. That also means it's irrelevant for gay couples to join in marriage.
Your CONstitution cannot protect a contract yet to be established, and same sex couples cannot enter into a marriage contract because they do not fit the qualifications based on the fact that they are if the same sex. They may however contract a same sex partnership that mirrors a marriage contract in wording other that certain references to the sex of the individuals must be changed, as a man is not a woman, a husband is not a woman, and a wife is not a man. Once those terms are changed to fit same de couples, it is no longer a marriage contract, but rather a civil union partnership, and that contract holds the same protections under Article I section 10. The obligations of any contract not yet established can possibly be impaired, because it does not yet exist.
Now, I have typed this very s l o w l y so please read very slowly so that this time you may grasp the facts presented.
Out of curiosity, you keep using the word "your". "Your Constitution", "your SCOTUS", etc. I take it you are not a US citizen?
I shall explain.....
It is a self evident truth that governments are instituted among men deriving their just powers from the consent of the governed.
I was born, and reside in Tennessee, I am a Tennessean, hence an American citizen. Your U.S. Government claims me as a corporate U.S. Citizen by birth via your 14th amendment. I do not willfully grant my consent to your U.S. Government, nor do I willfully participate in any way in Your governments political process. Hence it does not have my voluntary consent to govern, thus is not my government, I am simply coerced to live under it via duress. See Blacks law dictionary for the definitions of coercion and duress.
The system of government that exists today is not that of the founders' nor that of the framers' of your CONstitution, it is a perversion thereof.
