Jeffrey J. Sargent wrote:

Irrespective of one's views on gay marriage, there are two related
reasons why the Constitution -- any Constitution, but especially
the U.S. Constitution -- should *not* prohibit gay marriage,
should indeed be silent on the issue. If one is a true American,
true to the ideas and principles on which this country was founded,
and committed to "preserve, protect, and defend the Constitution
of the United States", one must oppose any such amendment,
and here are the two reasons why:

First: Since most who oppose gay marriage do so on religious
grounds, it follows that imposing a ban would be an establishment
of religion. The First Amendment clearly states, "Congress
shall make no law respecting an establishment of religion, or
prohibiting the free exercise thereof." A ban on gay marriage
would establish the religion of those who oppose it, and prohibit
the free exercise of the religion of those who think it's OK;
therefore such a ban is unconstitutional. And since the
Constitution(Article VI) calls itself (including any amendments,
per Article V)"the supreme *law* of the land", it follows that
making such an amendment would be making a law, and therefore
it would be unconstitutional even to attempt to amend the
Constitution in this way.
Second: Though I do not agree with Ayn Rand's entire school of
thought, she hit the nail on the head in the following passage
from her essay "The Nature of Government", first published in
1963:"Today, when a concerted effort is made to obliterate this
point,it cannot be repeated too often that the Constitution is a
limitation on the government, not on private individuals -- that
it does not prescribe the conduct of private individuals, only the
conduct of the government -- that it is not a charter *for*
government power,but a charter of the citizens' protection *
against* the government. "The proposed amendment flies directly
in the face of this obvious but widely ignored fact.
Again, if you wish to stand for what America really, historically
stands for, if you wish to follow proudly in the footsteps of
the Founding Fathers rather than spit on their memories, you must
oppose the anti-gay-marriage amendment -- even if you yourself
abominate the idea of gay marriage. It is the only logical
choice, the only thing consonant with the Constitution.
-- Jeffrey J. Sargent,