Of course it's a silly question.
Ask one of the framers of the Constitution whether marriage meant a man and a woman, or maybe two men. Would he think that was a sensible question? Yet for some reason people retreat to the documents of those very framers for shelter from their own silliness.
Thankfully, those venerable gentlemen realized they would not be able to legislate sufficiently for all time. So, in the Constitution itself, they left an Amendment process to revise it.
Unfortunately, we now seem to have people who think we're being disloyal to our very government when we follow the exact process of amendment laid down in our Constitution.
Is the power to define marriage left to the states by our Consitution? Technically yes. Is this same power left to our amendment process? Also yes. Since the objection being raised regards the invoking of the amendment process to define marriage, why is the same objection not raised to object to the states doing the same?