Exactly.
Or, to use another analogy, if a court, or the Congress, or a state, decides that up is down and down is up, there is no legitimate obligation for the other officers of government - in the other branches, or at other levels - or for the people of this country, to then go jump off 80-foot cliffs with them. Because the rocks at the bottom of the cliff won’t care at all about their silly, arbitrary opinions or lawless “laws.”
The Constitution is about law and the powers of the Federal and State governments to make law and regulate. It does not attempt to prove or disprove the existence of anything. You have no argument with this line of reasoning.
Powers that are not “expressly” assigned to the federal govt fall to the states. The Constitution does not “expressly” assign the power to determine the legality of abortion or marriage to the US govt so it falls to the individual states. You should agree with this because right now the Federal govt is controlling both abortion and gay marriage and guess what they are both legal in all 50 states. So you can rage on about it all day long but it would still be better if even half the states could reject these two abominations.