“The Court is making the preposterous assumption that the People of the United States somehow silently redefined marriage in 1868 when they ratified the 14th Amendment.”
Ignorant nonsense.
The 14th Amendment means exactly what it says, as originally intended by its Framers, and as correctly interpreted by the Supreme Court:
All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside. No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.
And that includes marriage law, where for the state to seek to deny same-sex couples access to marriage (contract) law they're eligible to participate in, is in fact a violation of the original intent of the Amendment's Equal Protection Clause and its current jurisprudence.